How many listings do you have?
Even if you delete the images from Auctiva, you will still have remnants left due to the HTML.
If you don't want the images in the description, do not load them to the Auctiva section of the listing (top portion), and only load them to the Ebay section (lower portion)
Once the item is listed on Ebay, delete the images from Auctiva.
It will still allow the images on Ebay but not in the description.
Do 1 as a test so there are no issues.
Once you have the images in the Auctiva section (description on listing) the only way I know how to remove it is to edit the listing in HTML and delete anything to do with Auctiva, which can be very tricky and very time consuming.
If you want to see what happens if you just delete the images, do one as a test to see what it looks like afterwards.
No matter what you do, it is easier not to include the images at the beginning when you do the listing, but still more work than just leaving them there.