Is it possible to add images in the middle of a listing?

Ummm...I'm not sure ebay policy would allow for that...it almost sounds like a 'choice listing' which in this case wouldn't be allowed. Not to mention you might have unhappy buyers on your hands, thinking they're getting everything pictured ( my pet peeve is People Don't Read ...myself included sometimes )

As far as the actual logistics of your question, I would think it's possible, but I don't know how it would be done

I believe member_8880 makes a very good point. There should be no confusion about what the buyer is getting (which pics of variations can create), and "choice" listings are specifically not allowed by ebay. Ebay does not allow multiple items on a listing unless they are either (1) identical items sold in a dutch auction, or (2)identical or similar items sold as a lot.
ebay:
http://pages.ebay.com/help/policies/listing-choice.html

http://pages.ebay.com/help/sell/multiple.html

Technically you can accomplish what you want by inserting the photos into the description manually. You can even have captions. This thread explains how:
https://community.auctiva.com/eve/forums/a/tpc/f/5796099...731047622#4731047622

Thank you ninth........I couldn't find those darn links

Many thanks to both member_8880 and ninth_wave for your time in responding. I have checked out ninth's links and what I am hoping to achieve doesn't come under the choice policy as I don't want to offer buyers a choice just point them in the direction of other similarly designed items.

I have had a lurk through various eBay helpy bits and found something that provides HTML code to add a link to a search within your shop so I have added this into a couple of items and then checked them out. When you click on the link (which says something like "Check out my other dolphin items") it runs a search on all my listings and then throws up another window showing all of the items that meet the search criteria. Although it doesn't get the actual item pics into my listing, it does achieve what I wanted which is to get people to see other items in my shop - fingers crossed it results in some sales.

I did spot a little bit that said you could add a picture to the link which I shall investigate later on.

Cheers again for your time and effort - keep up the good work!