The board is probably about the same size as a Macintosh LC board, but there is nowhere near enough room in there for an optical drive, 2 speakers, the logic board and a power supply. Not to mention all the supporting wiring. (PSU extenders, switches and long IDE cables)
Wouldn't exactly look too good underneath the TV or as a desktop server either... unless of course you hack the foot off and paint it black. Like an interactive television box but narrower...
I could throw it into a DVD player case, or a stereo tuner case. I have a spare one of each.