I'm looking for input over at imagecache actions.
I simply don't know or use imageMagick (as the servers I deploy to don't have it it's no use to me) but if you have anything you think could be reflected over to the imagecache actions or imageapi projects, that could probably be folded in happily.
Looking at the code here so far it looks like it's still just on the drawing board (so to speak).

If you can help us get (at least) image_overlay working in imageapi, that would be cool. Better (I think) to have these processes together rather than one library for gd and another for imagemagick like this. That's what the imageapi was trying to do, anyway.