Feel free to keep an eye on the Release Notes forum
as we are updating the Auctiva software almost daily. I'm currently in the process of implementing a workaround to retrieve different images sizes from eBay for listings imported/not created in Auctiva because of this eBay API issue (the fact that the eBay API does not return the originally uploaded image size, nor have an ability to request different image sizes via the Trading API). If all tests out ok, look for a software release soon to circumvent this eBay issue. We will still work with eBay to help correct the API (or at least extend the API so different image sizes can be retrieved programmatically). You are correct this eBay issue has been around for a while, so I'm hopeful to have a resolution soon.
We are glad you liked Auctiva and have been with us for quite some time, we continue to enhance and update Auctiva in ways that make selling online easier, solve problems for ecommerce sellers, and ultimately provide value to you.