Samejima, you bring up a good point about people that might have their group window 3x2 and we know how sensitive people are to change.
Plus I don't really like the idea of moving UI elements within our code. Makes it harder to mod the UI.
Drumstix, I definitely think I'm going to keep the icons 21x21. Being a stickler for straight lines and "evenness" I was really excited when the icons lined up perfectly with the progress bars. The bars are 109 pixels wide if you want to keep the textures at a 1:1 ratio and 5 icons at 21 pixels each plus 4-1 pixel separators is exactly 109.
Yes, the things that make me happy qualify me as a weirdo. =)