I have a suggestion, maybe you should add a section where other sites can advertise, if you don't like people coming just to do that (i know it can be annoying) then maybe youcould put up a rule that they can only advertise after so many posts. I might bring in more people
Also maybe a place for people to just chat about things none sim related, i know you have a picture board for non sim related stuff and a quizz board, but maybe a lace to just have a chat with other members would be nice as well.
Of course these are just suggestions and it is your site, but i just thought id try to help