Board Thread:Support Requests - Getting Technical/@comment-1020939-20140304004847/@comment-1693968-20140305023736

Like Fandyllic said, DPL won't work inside of a gallery tag. I don't know of anyway you can use a category to populate a gallery, but you could contact Wikia for more information.

If you're wanting to use DPL, you can look at the documentation here and here. I don't see anything about files in there, but you can check and see if I missed anything.