We have a couple of pure demoscene parties here in Sweden still. Pure demoscene is perhaps wrong, but they have banned gamers (unless they play retro games). For example, Little Computer People which is very, very retro, aiming mostly for C64 and a little Amiga. Then you have CompuSphere and Underscore. Each of these events draws about 100-200 people, 90-98% from Sweden and the rest from other countries, mostly Northern Europe.
To up attendance a bit perhaps the scope doesn't have to be demos, but demos and retro. Just meeting other people with similar interests might be a factor here.
Good luck with your party, and I hope to see some news regarding it during 2006.
http://www.lcp.c64.org/http://www.compusphere.org/
