Its a 64x64 spray, it looks a little grainy ingame but you can definitely see that it is indeed Bill Nye, and it is indeed spinning. Inertia is a property of matter.
Updated: Removed the green halo that he had. He's still fairly grainy but there isn't much that can be done outside of resampling his head spinning into 5 frames at 128x128, the current animation is an 8 frame spin and thus the max size that can be used is 64x64.
Pros: Brings back the good ol days of middle school science class.
Cons: You said it yourself, "looks a little grainy ingame" add the effect of the green outline and the result is a real eye-sore.
Improvements: Clean it up a bit, especially the green outline.
Notes: If it's to hard to find a clear and high resolution pic, then why not try to recreate it tf2 style with a few filters?