MyBB Community Forums

Can I have two different themes working together? I want to employ one special theme for my portal page while a second theme to treat rest of my site. Possible?

I think the closest to this that you can get in mybb is to set a different style for individual forums. I think that this will allow you to make forum view, thread view and posting-related pages different from the main theme, however that still leaves non-forum-specific pages like user cp. It wouldn't be too hard to code a modification to enable such behaviour, but at the same time it's doesn't come as standard.