the one that would create the most interest is sexy pics of your truck with good lookin ladies or gentalmen (for you ladies) posed in in, on or by the truck.
Or a good one would be to post pics of you wrenching on your truck. I won a rig of the month comp on a powerjoke forum with pics of me standing knee deep in the engine bay covered in grease from head to toe. There were plenty of other great pictures.
I also think that the VIN number poker was a very clever idea as well.
Pictures of you Jumping your truck, everyone has the balls to drive through the mud or over some rocks but not everyone is crazy enough to jump their truck! (including me)
Donuts post pictures of your best donuts or the after math there of.
Mud bogging is one of the most fun forms of offroding imo and the trucks always look great covered in mud for a day or two.
Dirtiest rig, take picsof your dirty rig who ever has the dirtiest wins.
trucks being cleaned Bikinis, speedo's what ever your flavor is.