Any differences between PhotoBucket or ImageShack won't make any difference for solving your difficulty with posting self-hosted images on eBay.
Have you looked at Auctiva for image hosting and description posting?
http://www.auctiva.com/default.aspxUsing eBay's image hosting service is like going to a restaurant and letting them do the cooking, but they do charge for the services provided.
Posting multiple pictures using html on eBay is like buying groceries and cooking at home. Cheaper, but you have to learn how to cook.
Here are some basics on learning how to "cook" html:
http://www.w3schools.com/html/html_primary.asp