Hello again SpunkyBob -
Please note that we have bulk tools available for Saved and Active listings. It sounds like you are referring to your already active listings, and you should be able to make your updates to listings that are eligible for revision on eBay using the Bulk Revise tool on the Active Listings page of your account. In that tool there is an option for updating the description, which is where the images are (excepting the Header and eBay gallery images, which eBay makes copies of so they should already be HTTPS) and if your images are Auctiva hosted or hosted on a secure server (if you use a custom template for example) you should be able to use the Find and Replace tool for the descriptions to update instances of http to https as needed.
Please also be aware that at this time we are experiencing a heavy support load so it is likely that there will be a delay in our response to your case as we respond to support cases in the order that they arrive, but we will respond to you and the specifics of your case just as soon as we are able.
Thank you for your patience.
- Craig