I own a small $10 lightbox that I purchased on ebay (Chinese manufacturer) and it works just fine. Looking back I just wish I had ordered abigger one, because, even though miniatures are not that big, fitting a backdrop in the smaller lightboxes can be really limiting.
The one I picked up is this one:
http://www.ebay.com/itm/24-60cm-Light-S ... SwjVVVjQei
The size problem eliminated itself pretty much after I bought some additional studio equipment. My current "lightbox" is livingroom sized with backdrop system, light stands with remote controlled lights, softboxes and umbrellas. The works.
At the moment I use this backdrop. These are not miniatures, but the picture illustrates what I'm talking about a bit.
DSC_4238 by
b j, on Flickr
DSC_4223 by
b j, on Flickr
What I used there was a Neewer 9ft backdrop system supporting a 4'x4' rusty sheet of metal, 2 remote flash units on light stands bounced off the wall and ceiling and sheet of glass on a black cloth used as support.
A lot more fun then a lightbox, but quite a bit more expensive, and it takes away more space.