umm - smf default is still there to chose.
As for any other themes - we'd need one that would allow us to have our own top bar for the wmw menu, so not everything qualifies.
Also we made some modefications that need adapting.
We had at some point several more themes installed wich I got rid of after noticing that nobody ever used them...
Anyway, we've been discussing redoing the complete forum with the upcoming release of smf 2.0 but atm our recources are spare.
Basically it's just me, and I've got an hour or two to give on the weekends atm - which are IMO better spent doing something else
So - for now you gotta switch to smf default or just live with the old one