These are my initial thoughts on the limitations proposed, feel free to share your thoughts as well!
TWO COLORS - could be fun, but I hope it doesn't get too samey with people using the same color schemes or art styles
ICE AS A MECHANIC - that's a good possibility space, could be fun to see what twists people could come up with with ice.
MUST NOT UTILIZE SPRITES - kinda vague on what counts as a sprite, since fonts are made up of sprites, but most people would use text. Making the engine render all game assets from scratch would be challenging and fun but extremely hard!
2 MECHANICS - vague on what is a mechanic, since "pause" and "jumping" already cover two mechanics but "shooting" and "moving" also do.
SIDE SCROLLER - not very limiting, 99% of games have side scrolling in them. AUTO scrolling however, could be very interesting.
SURPRISE LIMITATION - that's not very democratic, but I like surprises.
64x RESOLUTION - extremely limiting, I'd really like this theme just for seeing what I can come up with. Has a 3D 64*64 game been attempted yet?