First let me thank you for the awesome mod! Great work so far, I'm almost back at pre-vB4 performance. I'm looking forward to the showthread update.
I'm trying to add custom images to the sprite sheet and I'm not able to add more than 1 for some reason. I used the instructions and created 2 plugins for 2 icons. When running Refresh (should be named "Regenerate" or "Rebuild") it does show Custom icons: 2, but it only adds one to the sheet and throws a path error for the second. For some reason it adds the local server path "twice" to the second icon. I'm using the full and same url in both cases, just the image file names are different. Any ideas?
Also let me know how I can make a donation (edit: duh..., must have logged out or something and missed the option.)
On a similar note, and I'm sure there are plenty of other good ones, I'm using
http://www.websiteoptimization.com/services/analyze/ to analyze the results online.