I checked in skin diffs support that lets you compare your version of a skin to the original skin.

Here's a screenshot, I couldn't upload it to this site because of the gif upload bug (which is fixed in CVS, too, btw).

The code is in the need_for_speed branch, which is my current working branch. Please help me finish need_for_speed, a lot needs to be done!

You'll need a fresh Helma build to run this, since I just checked in Diff support for Helma.