I'm not sure what you mean by "Auctiva already got slapped on the hand for this", as we do not control the images that are placed in our customers' listings. Regardless of whether you are posting through Auctiva or directly through eBay, you do have the capability to specify header/gallery images that represent a completely different item than the images within your description reflect. However, doing so would obviously not be conducive to maximizing one's sales.
In any event, if you need to change the gallery/header images specified in your listings after they are active on eBay, you will need to make that change through eBay's "Revise your Item" form. This specific revision can be done via the following process:
1) Log-in to your eBay account and visit the item for which you'd like to change the header/gallery image.
2) Right-click the image you’d like to make your new header/gallery image and click “Properties”
3) Copy the image URL, which begins with http://..
4) Click the “Revise your Item” link at the top of the auction page.
5) Click the “Add Pictures” button.
6) Delete the text(if any) in the “Enter URL…” field(if any) and replace it with the copied URL.
7) Click the “Insert Pictures” button and save your changes.
Any additional questions or concerns? Please feel free to contact our customer support team using the appropriate link on our help page: http://www.auctiva.com/free-auction-software-help/help.aspx