Why not use AirPlay mirroring from your iDevice to AppleTV?
What I do for videos is use AirVideo which streams my video content from my PC to the Apple TV via iPhone or iPad.
I take all my pictures with my iPhone 5 so turning on Photostream on the AppleTV takes care of that.
Because mirroring is not the same, it's not an icon right there beside the play/pause button.. i have to double click home slide over a couple of screens and select it. it doesn't fill the screen as well as airplay. i find it stutters sometimes when airplay never does. and the biggest difference is airplay allows multitasking, the video plays on the tv while i can do other things on my phone or ipad.
i simply want to be able to airplay photos in my dropbox like i would photos in my camera roll. and airplay videos in my dropbox like i can videos in youtube or almost any other app that has streaming video.
is there possibly another app, a media player of some kind, that reads files from your dropbox? kind of like plaintext allows you to edit text files in your dropbox?