Conn, to insert photos that you host yourself, go to the box that says "describe the item you're selling" on the listing form click on "html" and insert your link in the following format:
<img src="http://yourdomain.com/yourfolder/yourimage.jpg">If you have all the connections right (nothing misspelled, no mistakes, when you click on "standard" your photo should load into the form. If loading more than one photo, use the html code <p> between them.
To get your photo to show in the gallery, click on "add pictures" above the description box and choose "self-hosting." There you only need to add the url without the dressing, meaning without the quotes and the html brackets and code, like this
http://yourdomain.com/yourfolder/yourimage.jpg.
Hope that helps you.