Hiya,
I'm quite new to this UBB stuff so maybe this has been told a lot of times before, is off topic or complete bullshit. In this case, take my apologies in advance. ;-)
When hacking the css/templates I wondered why there is absolutely no use if the so wonderful 'id' attribute all xhtml tags have. This makes it almost completely impossible to do any css-skinning beyond basic stuff like colors, borders and fonts.
It would be nice to have a unique ID for the different tables so they can be rendered at different locations, be replaced by images, made invisible, ...
IMHO all calls to 'tbopen' should include (an optional) id.
As a second step you should consider bloating the number of style classes used and make use of style class derivation. So the 'stylist' has the posibility to style the 'reply' button different from the 'continue' button an so on.