"Image ID of your commissions sheet (optional but recommended):"

Maybe this is a dumb question, but how do people upload multiple image IDs to this? Most commission listings have two or three linked images in them, but when I try to post multiple it gives me an error. Thanks.

The commission sheet is the large image at the top of the commission listing. After you create your listing, you can add various commission types, each with their own image

@Joey  
oh, so if you leave it blank it just uses those. Thanks.