When I list items for sale on eBay, I use a custom-developed HTML template with the item's pictures uploaded externally and embedded into the description for more visual appeal than what eBay provides. This allows me to apply custom styles to the images via CSS, provide descriptive content below specific images and generally offers a lot more flexibility and professionalism.
By default, eBay allows you to upload up to 12 images for free to be included in the ad, and requires uploading at least one image through their service to be displayed in the auction results and so forth. The images uploaded in this manner appear at the very top of the auction page alongside the auction metadata. These eBay-hosted pictures are scaled to 500x375px regardless of the user's screen resolution, with an option to view larger versions by clicking/hovering over them.