The green eye is really hard to see against the yellow body
Blue would probably work better then.
I have an Idea for a critter flying.
You need ASM though. Find the values of the booster fuel and the speed of flight (I can't help you with that, you should go on the CS forums). Then go to the spriteset that has the graphics of the booster particles, and erase it. Then you need a sound editor, so change the booster sound to a flying critters'.
... What does that have to do with spriting?