How about an adjustment for exactly how rounded that tail is? Color options for that fire?

That gradient tool will be handy. I never liked how filling smooth shapes always looked glitchy even with high tolerance on the paint bucket tool. I do worry that we will see a plethora of cursors that are simply arrows with gradients, unoriginal at all in the gallery however.

And although it is the month of weight loss...
Whenever I have animated something that rotated (For example the beam in my radar cursors), I had to copy the original object to each fram and then rotate it say 5 degrees in the first frame, 10 in the next, and so on. If I simply created a new frame from the previous one and rotated it another 5 degrees, another 5 degrees, etc. the object became blurrier and blurrier as a result of simply being a rotation of a previously rotated object. Thus I had to always start with the original frame.

Perhaps a wizard or other tool could be created that would allow for an object to be a rotated throughout a series of frames. You would pick the starting and ending frames and the amount that it should rotate between them. It would automatically utilize the first frame but save the user the work of having to manually copy it and rotate it throughout the animation.

Fire color will be controlled by the user. The roundness of the arrow tail probably won't. It is not really round, I just cut the corners and because they are very small, it looks round. Making it adjustable could produce weird results (but it is javascript and can be tweaked be users.)

The gallery will suffer and I expect there will be a lot of deleting going on. Maybe I would make the gallery upload page harder to access, possibly requiring the users to pass a short test, where they would have to prove they understand the basic rules.

The rotation wizard sounds like a neat idea and it should not be too hard to do. I would implement it slightly differently though: user selects 1 layer in 1 frame, runs the script, selects total rotation amount (usually 360 degrees) and number of intermediary steps. The script duplicates the frame and rotates the selected layer in each frame. Would that work?

Oh, and about the filling. These scripts draws the interior and then the outline over it, but that is usually not how a humans create drawings. To fill a shape as smoothly as possible, I would recommend to set tolerance to 99% (or as high as possible) and use the Paint Under blending mode.