Yup, it's basically just a cardboard box with hollow sides, with tissue paper wrapped around it. That way when you position a lamp above the box, the tissue paper spreads the light evenly throughout. Pretty sure Lord Oblivion's got a picture of his one in his Flickr photostream if you're interested...
Oh, and photo editing really makes a difference for good-looking pics. I usually just up the brightness and contrast levels a bit.
I can't use boxes. With MOCs as big as mine, either height wise or length wise, I'd need a pretty damn big box and a lot of tissue paper. I sometimes photo edit my pics to, generally just saturation to return the color my camera sucks out of the MOC and a bit of brightness Most of the time I don't even think about editing the pics, I go straight from snapping the picks, viewing them on my computer,deleting crappy ones, and uploading the few I like. If I do detail layouts I edit them since I'm using the same program anyways.
Yes, they're pretty big, or some of them are anyways, not all of them are. Some people forget or don't even pay attention to the fact I've got regular sized MOCs.
Well with my current set up I've got a desk lamp that I shoot from the side, and one of those room lamps on a poll that I'll stick in front of it. It works alright but I think from above would work well to. Plus I've got to use a sheet so there's wrinkles that cast shadows in the background. I was using a white one but it made all my flashless pictures look very yellow in tinge. I find the light gray one fixes that. Its a good medium color. Silver and grey blends in a little bit but not too bad.