I would like quite a few effect plugins created, here are some:
Create Palette from Image - Can create color palettes from a range of 10 to 256 colors, and one image.
Recreate Image from Palette- Can recreate images from a range of 5 colors to 256 colors, and also select what colors out of the total number of colors can be used.
Add Noise - Can add noise to an image with a amount slider bar.
Suggest what you would want here, too!
Can you explain what is the actual purpose of the first two plug-ins? I am not against them, but I would like to understand what you are trying to achieve - perhaps there is simpler way to that. Are you trying to manually optimize GIFs or is your goal an artistic effect?
I believe there already is something like the 3rd effect, but it is just a scripted effect.