I have been using a lot of WebGL shaders for my personal projects.
My requests are mainly hacks to existing effects.
Noise- Have a speed control. I am trying to add noise to a canvas snapshot and I am getting scan-refresh lines. It would be nice to have the noise Stop, or variate the speed.
Emboss - Give a light source direction. Right now it defaults to the light being in the lower right corner of the image. This makes it completely useless for side scrolling games where the light source (eg, the sun) would be coming from above the game board.
Blur- Combine horiz and vert blur into a single block. Make it so it is Horizontal, vertical, or BOTH. Trying to knock the high spots off an emboss is a real pain in the butt when you have to add 2 effect blocks every single time you want to do a "blur-all".
Glow- Combine Horiz and Vert Glow so we add, and adjust BOTH at the same time.
Render Normal map- with complete control over the RGB channels, so you can make Green up for Maya or Blue up for Blender materials. This one needs to be tileable as well.
Render to color pallet- For making everything from CGA to early VGA games with a pallet. User supplies the pallet as a bitmap like NeoTextureEdit.