I think an mpreg board would be kind of pleasant for a number reasons
1. As far as I know there is no mpreg imageboard so this would be the first and probably the only one for awhile.
2. It's a big subject with many different topics i.e. gay mpreg, straight mpreg, mpreg stories, mpreg fan art, mpreg comics, mpreg morphs, I could go on and on
3. It would organize the site better, someone looking for mpreg wouldn't have to go through what is irrelevant for their search if they want to browse
4. I think people would be more comfortable to post and talk about mpreg if it feels like you're around like minded individuals and not have to worry about the people who aren't into it