I see you have added some other file upload attributes to your test product already.
A few questions to help you organize the presentation: Are these banners all black on white? If not, how will your customers tell you which image is supposed to be green and which one is supposed to be blue? Will double-sided or multi-color banners be listed under the same product id, or will they have separate identities?
If someone is ordering several identical banners, just having a quantity box and one or two file uploads and color choices will work fine. If someone wants two of one design and one of another, asking them to upload the first image twice, or tell you verbally which one to duplicate, seem like poor solutions. They can order as many of one version of a product as they want in one "add to cart" operation, then go back and add another set of options; the two non-identical versions of the same product will appear separately in the order. (There is or has been a bug in the logic that can sometimes mess this up, but it can be avoided by displaying the options in a certain order. If you run into this, search in the forum for the solution.)
In summary, my general advice is to have only one or two file uploads (depending on number of sides the product may have) per product page to make order variations simpler.