PAM modules that are referenced in the configuration files can be located with this command:

ls /lib/*/security

returns:

pam_access.so     pam_keyinit.so    pam_permit.so      pam_tally.so
pam_debug.so      pam_lastlog.so    pam_pwhistory.so   pam_time.so
pam_deny.so       pam_limits.so     pam_rhosts.so      pam_timestamp.so
pam_echo.so       pam_listfile.so   pam_rootok.so      pam_umask.so
. . .

Look in this directory to see what kind of modules are available to use.

Almost all of the modules have man pages, which can describe their usage.