Krezk and Levkarest in Borca would add a lot to Barovian gaming since they're not technically too far. I think that more than new realms, at the moment, we would need more Barovian towns, or boundaries ones, not to have the people overtly spread all along the server (Teufeldorf and Zeidenburg would be nice too). My two cents.
Not as far as town, but as areas, I would like a Forlorn border with really nasty hordes of Goblyns. It would give a sense to go there for "war-like" activities.