If the pictures are hosted on eBay servers, you can list an item with multiple pictures using AddItem.
If you host your own pictures, then you can send in only one PictureURL in the PictureDetails container . If you send in more than one, the first one will be used and the rest will be ignored. The only way to add more self hosted pictures, is to use HTML content in your description and add the remaining pictures that you need using the img tag.
Now, you can use the PhotoDisplay option, only if the pictures are hosted on eBay.