pveam available

returns:

mail            proxmox-mailgateway-6.4-standard_6.4-1_amd64.tar.gz
system          alpine-3.11-default_20200425_amd64.tar.xz
system          alpine-3.12-default_20200823_amd64.tar.xz
system          alpine-3.13-default_20210419_amd64.tar.xz
system          archlinux-base_20210420-1_amd64.tar.gz
system          centos-7-default_20190926_amd64.tar.xz
system          centos-8-default_20201210_amd64.tar.xz
system          debian-10-standard_10.7-1_amd64.tar.gz
system          debian-9.0-standard_9.7-1_amd64.tar.gz
system          devuan-3.0-standard_3.0_amd64.tar.gz
system          fedora-32-default_20200430_amd64.tar.xz
system          fedora-33-default_20201115_amd64.tar.xz
system          fedora-34-default_20210427_amd64.tar.xz
system          gentoo-current-default_20200310_amd64.tar.xz
system          opensuse-15.2-default_20200824_amd64.tar.xz
system          ubuntu-16.04-standard_16.04.5-1_amd64.tar.gz
system          ubuntu-18.04-standard_18.04.1-1_amd64.tar.gz
system          ubuntu-20.04-standard_20.04-1_amd64.tar.gz
system          ubuntu-20.10-standard_20.10-1_amd64.tar.gz
system          ubuntu-21.04-standard_21.04-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-ansible_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-asp-net-core_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-avideo_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-b2evolution_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-bagisto_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-bugzilla_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-cakephp_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-canvas_16.2-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-codeigniter_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-collabtive_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-concrete5_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-core_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-couchdb_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-django_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-dokuwiki_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-domain-controller_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-drupal7_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-drupal8_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-drupal9_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-e107_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-elgg_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-espocrm_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-etherpad_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-ezplatform_16.0-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-faveo-helpdesk_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-fileserver_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-foodsoft_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-foswiki_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-gallery_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-gameserver_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-ghost_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-gitea_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-gitlab_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-gnusocial_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-icescrum_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-invoice-ninja_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-jenkins_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-joomla3_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-lamp_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-lapp_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-laravel_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-leantime_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-lighttpd-php-fastcgi_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-limesurvey_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-magento_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mahara_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mantis_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-matomo_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mattermost_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mayan-edms_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mediaserver_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mediawiki_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mibew_16.2-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-moinmoin_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mongodb_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-moodle_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mumble_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-mysql_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-nextcloud_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-nginx-php-fastcgi_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-nodejs_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-observium_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-odoo_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-omeka_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-opencart_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-openldap_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-openvpn_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-orangehrm_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-oscommerce_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-otrs_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-owncloud_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-phpbb_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-phplist_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-plone_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-postgresql_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-prestashop_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-processmaker_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-rails_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-redis_16.2-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-redmine_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-revision-control_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-roundup_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-sahana-eden_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-silverstripe_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-simplemachines_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-snipe-it_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-suitecrm_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-symfony_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-syncthing_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-tkldev_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-tomcat-apache_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-tomcat_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-torrentserver_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-trac_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-tracks_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-typo3_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-ushahidi_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-vanilla_16.1-1_amd64.tar.gz
turnkeylinux    debian-10-turnkey-web2py_16.1-1_amd64.tar.gz

For example basic system images:

pveam available --section system

returns:

system          alpine-3.11-default_20200425_amd64.tar.xz
system          alpine-3.12-default_20200823_amd64.tar.xz
system          alpine-3.13-default_20210419_amd64.tar.xz
system          archlinux-base_20210420-1_amd64.tar.gz
system          centos-7-default_20190926_amd64.tar.xz
system          centos-8-default_20201210_amd64.tar.xz
system          debian-10-standard_10.7-1_amd64.tar.gz
system          debian-9.0-standard_9.7-1_amd64.tar.gz
system          devuan-3.0-standard_3.0_amd64.tar.gz
system          fedora-32-default_20200430_amd64.tar.xz
system          fedora-33-default_20201115_amd64.tar.xz
system          fedora-34-default_20210427_amd64.tar.xz
system          gentoo-current-default_20200310_amd64.tar.xz
system          opensuse-15.2-default_20200824_amd64.tar.xz
system          ubuntu-16.04-standard_16.04.5-1_amd64.tar.gz
system          ubuntu-18.04-standard_18.04.1-1_amd64.tar.gz
system          ubuntu-20.04-standard_20.04-1_amd64.tar.gz
system          ubuntu-20.10-standard_20.10-1_amd64.tar.gz
system          ubuntu-21.04-standard_21.04-1_amd64.tar.gz