I personally just have all my WIP (and finished) projects in one thread (terrain, sculpting/converting, painting), but I cannot update it very often (once a month usually).
If you update it more regularly, you could have a few threads, one for painting, one for sculpting/converting, and one for terrain. Or, alternatively, you could of course go for one larger thread per project (say, a Moria project has one thread, one thread for a Harad project etc). Just whatever you feel is best, I guess.
Doing a campaign sounds great though! A behind the scenes makes sense then, and another thread for the reports would be cool (or perhaps some articles?).
As for the campaign itself: what will it be, and how will you do it? If you need some ideas about a campaign, I have loads (as I've been working on a fan supplement on map campaigns), so just ask if you'd like some help or ideas.
Good luck!
