I have two GIF files, three modules (pm files)...

If the GIF files are in a known location relative to the .pm file, you could use Perl's __FILE__ variable in the .pm file. For example, in the Photo method, if a bald file name is given, you could look for that file in a directory relative to the .pm file (that trick is used by Acme::EyeDrops to find the .eye files relative to EyeDrops.pm).