Would the admins make a sub-forum for "Miscellaneous Interests" such as hobbies, travel, pets, books, movies, etc. or whatever daily-life thing people would like to post about? I'm thinking it might help folks connect in a way that would focus on things other than JUST poly-amory... that is after all how it works in real life. You don't build relationships based on the fact that you want a relationship... you build them based on common interests and mutual inclinations.
Other forums that I belong to have a "Misc" section. I have looked over this one and every sub-category seems directly related to poly, but it is exactly other parts of life and variety thereof that impels one to consider poly in the first place.
For example, I would prob'ly share about cat-things, camping, cooking, music and books that I like, and my other interests even though it doesn't directly have to do with integrating poly into my love-life. These are still the things that make us who we are and that is what relationships are supposed to be about.