MuffinTopKnits, I have a good tip for you that is not really related to the light box issue, but since I've reviewed your shop for other threads, here it is..
Make sure your pictures are AT LEAST 570 pixels wide. They should be slightly wider than tall, so that Etsy doesn't crop them. I miss the handle of the purse on some picture previews, and your purses have lovely handles so I don't think you want to miss that.
Maybe copy the size/dimensions from the first image in my listing, it comes out pretty well for shop views and treasuries:
http://www.etsy.com/listing/76443820/headband-flower-bouquet-of-carnationsI don't use a light box at all, a) not sure how to make one and b) the already-made-ones for photographers are expensive.. so I just take pictures whenever dutch weather is decent (rare!), putting my items on a white table, against a white wall and photoshop the lines of the background out..
Hope it helps,
big hug!
Carla