I recently bought 3 BW boxes. There are TONS of extra pieces in there, particularly the turrets and hard top that just beg to be converted into extra vehicles. Here's what I've done with them. I'm so pleased with the results, just had to post some pictures. Enjoy!
Old gorkamorka trukk spruced up with parts from the battlewagon's rear walls:
3 Killa kans from the grot turrets + grabba claw + a few bits and pieces:
3 Wartrakks from the main turret + hard case. I made the tracks purely from old gift cards and plastic tubing, wheels from a kids toy: