I'm currently working on a photo gallery, too, and i guess i got some interesting ideas as for the implementation.
my problem was, that i want to add several galleries.... a photo-gallery, a mp3-gallery and some other stuff... i didnt want to write every single gallery from the ground up as i don't have much time, so i had to find solution were i was able to make use of the similarities in structure.... let me shortly sum up what i did, maybe it can help you save some time
the most striking similarity is that all galleries will have categories, so i decided to make use of the functions already implemented in index.php and viewforum.php... i simply added another col named "gallery_type" to the "phpbb_forums" table. this gallery_type can be set in the admin panel to "forum", "photo", "mp3" or whatever you need. so if i add a "?mode=photo" to the index.php i will only see those forums that i marked as photo-gallery-type and BAM, the categories are finished

. now i only have to add a couple of lines to the posting.php, so that the "add new topic"-case is handled as needed in a specific gallery....so if you start a new topic in a photo-gallery-forum, you will see an upload script whereas in a normal "forum-forum" (

) you will see the usual post-form... as "replies" are handled in a different way, i don't need to change one line of code to get a "comment-function" for posted pictures or mp3's....
hopefully, this may help you when you start developing.... i will probably not be able to release my version as a mod... and before i forget, i'm sorry for my bad spelling
