I use those cheap aluminum work lights with clamps, and then use the bulb CFLs that are between 5000 and 6000 Kelvin on the color scale. This is crucial, and they used to be hard to find, but with more CFLs out there now, it's getting easier to find different color bulbs.
I think my whole setup only cost me like $30 including the lights. I used a 24" x 24" x 24" cardboard box, cut square holes in the top, left and right sides, cut the lid flaps off, then attached my sweep inside the box. I then taped large pieces of tracing paper over the square holes I cut out. I like tracing paper because it's cheap, and I can add more sheets if I want more diffusion.
I go between white and black backgrounds in the sweep (art stores have colored sheets of craft paper for cheap), but it's hard to keep the white clean from tire scuffs from diecast and RC cars. Usually, you can store the other sweep you aren't using underneath the one you are using, saving space and making your booth a little more compact.
You can also drape a white sheet over your pipework to create a simple, quick diffuser that should work really well.
The key to the lightbox is the lightbulbs and the camera settings. Oh, and a tripod is CRUCIAL, because the light that you will be using in a lightbox is not bright enough for fast shutter speeds. A slow shutter speed and a high F-stop (like f18 or higher) will give you nice, sharp photos that have a good depth of field.
Lots of trial and error to get good shots. I think I spent a whole day experimenting with camera settings and lighting before I got it where it was a point and shoot operation.
dc
A couple more for ya... far from perfect by any stretch of the imagination, but light years better than 99.9% of eBay photos.
