spin*.tiff are unused; that cursor is actually loaded from our resources file (for now; bug 358159 will change that, but probably to something else that will also not require those files as such). I'll audit the cursor-loading code for others that are resource-based. We seem to really love shipping extra copies of cursors.
Presumably this should be done in widget, then; all of those cursors come from the Cocoa cursors. That is to say, obviously we can stop shipping them ourselves for a few K win, but if they're not used, widget should not send them to dist/$wherever for anyone. I also worry about us being blindsided by some change if we stop shipping them alone.
Josh, do you know where the code that pushes these dummy resources to dist/ lives?