Not a bad idea. Go for it.
For me, posting and reading in a forum with a dark background/light font - is generally harder to read and contribute.
Keep in mind that forums can get out of hand sometimes. So learn how to control them. They also consume a lot of time for people, so try to make it worthwhile for them.
I suppose the front page for the domain -
3d Architectural Renderings - 3d Virtual Tours at 3D Magical Designs - looks like a business - doesn't quite fit in with a non-profit forum on the same domain. If running a business, I would come up with a separate domain and link back where appropriate.