1) Patrolling Behavior - This'd be something very standard you'd use in any 2d platformer for enemies or NPCs.
It should just set the sprite to go from x, y to x, y over a certain amount of time. It'd also be nice if we'd have a 'wait at x, y' value (so an enemy would go patrolling, stop to look around and go on patrolling again).
a) Animated Film Grain for a certain layer. To give everything an interesting effect. Just a slight film grain layer that'd work on certain layers. So you'd have film grain in the bg and over the sprites, but not over the HUD.
b) Light Flicker / Glow: Could be added to Lights or generally sprites - random flicker behavior that'd basically set a random value on the opacity of an object which an adjustable frequency, so we could create interesting lighting effects. Also, an added glow effect would be neat. So we could have a light and a glow on top of it, the light would be animated through the flicker and the glow would be animated through a randomizer to make a simple light feel a lot more atmospheric.