Once you have uploaded your photograph there is an option to specify Main Thumbnail Image, the Shapeways greyscale render will be called Default and all you need to do is select the image you would like to be used as the thumbnail.
Ensure you have a clear, well lit image cropped nice and tight to the object for the thumbnail image. We are always on the lookout for great designs that are well documented and we will only feature them on the front page or any other galleries if there is a suitable photograph as the thumbnail...
Ensure your images are 450x324 or 700x519 so they fill the thumbnail correctly.
If you want to sell your 3D printed designs be sure to open a Shapeways Shop and if you want to embed your Shapeways shop or favorites into another site check out the Shapeways widget.