Kier, can you suggest some of those programs which support the 8-bit versions of the graphic? It's obviously much more resource-efficient to use the 8bit than the 24bit.
I recommend Adobe Fireworks CS5. I always use it when working with web graphics and highly recommend it.
Bare in mind the more imagery you post within the spritesheet the higher the chances your going to result in images starting to suffer from quality being compromised. I can't see png-8 being used in the extended pack since more colors are being used unless you start splitting and breaking down spritesheets. I'm all for saving kb but when quality is being compromised for me it's not worth saving a few kb. Eitherway, no matter what route you take your going to be making compromises whether it's saving kb using png-8 and splitting spritesheets adding more http requests, quality loss or using 1 mega sheet png-24 with a higher kb.
Just curious, but why are the stars in there? I've never seen a part of XenForo that uses a rating system; mind you, haven't looked too hard but still.