There are a few forum themes, but not many. There's one for Simple Orange (and one or two others) over at squatty.com. Also, some themes (e.g. White Pointer, I think) come with matching forum themes already.
I'm not aware of a "monochrome" forum theme, though.
Also, Blaine has reworked forum theming for the 2.3 forum release, so it should be easier to make forum themes once that version is out.
bye, Dirk