Thanks for all your comments so far.
I pondered about another way to not waste valuable text-space.
I could add tiny buttons to the left side (M for Main, N for Npc, T for Tells, G for Guild, (second) G for Group, S for System and H (or ?) for Help)
_________________________________
M| Arerano says: Test
N|
T|
G|
G|
S|
H|_______________________________
| Input Line
Or maybe the buttons on the right side. But I am unsure how usable (user friendly) that would be.
I also tried a bit around with the guild window, but the background is hardcoded. Well, lets see with what I'll come up next. (currently also working on things which aren't GUI related - not in that way at least.)
btw, it matches Cherppow's Glass and Paper GUI skin perfectly.
Wow, almost looks like made for it.
However it seems like there's no indicator to see which tab is active.