I don't know if the theme for EF 18 has been decided yet, but if not, we could try to think of some things here...
EDIT: Mystifur says the theme has already been decided. But we can still suggest things for EF 19 instead?
Down Under, AustraliaAs long as we don't have too many Australians at Eurofurence this could probably be very unique. There could be panels about didgeridoo playing and other things specific to Australia.
The MayasKiantis suggested this on the IRC channel. It ties in very well with the year 2012 and there is plenty of story material for the pawpet show.
Space and science fictionThis year's EF touched a bit on the future, but we haven't really had anything like this before. A pawpet show in space would be really interesting I think. Maybe including time travel? Or maybe 'time' could be the theme itself?
The OceanThis would be a little harder to work out, but an underwater theme? It could be nice.
ArcticI think someone else suggested this. Perhaps combined with arctic culture, such as the Nordic countries (so the Swedes and Finns can laugh) or maybe northern Canada.
RussiaThere is a lot of story material in this and a rich history. It may be necessary to avoid references to communism, though.
Ancient Romans and GreeksFurry philosophers and circuses with fursuiters! All roads lead to Eurofurence of course. :p