Media in GeekShop

Can someone specify what the media limitations are for GeekShop? I'm talking about what the best image resolution is, how many images per product, etc that each listing can do. I'm sure I can do some tests on the existing examples but it would be helpful if you can just say what the dimensions and/or file size is best to use. Do these get resized automatically? If I'm using photos from a given product in Amazon for instance, they have wildly different resolutions. Amazon does this so that an end user can roll over an image and get a zoom. So is there some sort of advantage/disadvantage for using a larger image over a smaller one?

Thanks...