I’m interested knowing most of the somewhat hidden functions for the photo channel.
Here’s a list of functions I’ve found so far.

Photos:
D-pad up/down-Blurs-tilt left thinner, tilt right thicker.
Doodle: colors, objects, cut areas, eraser, ect.-get closer to increase size, get farther away to decrease size.
Puzzle: Hold 1 to change 48 piece to 192 piece.

Videos:

D-pad-same as photos. D-pad down-same as photos and makes every thing a higher pitch. 1-rewind. 2-fast forward. Can be played backwards.
Mood: Brighten-takes away some bass. Black/white-muffled (classical) sound. Zap-weird sound. Hard-boiled-Demonic sound.
Doodle: Same as photos.
Puzzle: Same as photos.

Mp3:Uknown.

Well done, you’ve found more than I have..;