Hi Solar,
Sure! You should be able to add a gallery image to this item via the following process:
1) Log into your eBay account and click on "My eBay"
2) Click on the item for which you'd like to change the gallery image.
3) Right click on the image you'd like to make your gallery image and click "Properties"
4) Copy the image URL...it begins with "http://..."
5) Click "Revise Your Item"
6) Click "Edit pictures & details"
7) In the "Gallery Image URL” field, paste the copied URL over the existing one and save your changes.
I hope this information proves useful. Please let us know if you have any additional questions or concerns.
-Mike