I got some help with unsticking the layers or... something. So I've got a blank template (background image and author name, no story title) I can use for future projects. Which is kind of what I expected to get from the cover designer in the first place, so... I'm happy! Of course, now I have to mess around with fonts for the title, etc. I'll see how sales go for this short story and decide if maybe I can justify spending $5 on a fresh cover each time... ETA: of course, I'm running a free giveaway on this story right now (that was the general idea, to just use it as a promo tool) so it's really not fair to judge it based on sales! Maybe I should just accept that $5 for a promo tool is pretty reasonable...
Personally, I'ver never gotten the hang of GIMP. I am fairly proficient in Photoshop, and GIMP, at one point, seems to be modeled after that UI-wise (and has since developed away, similar to LibreOffice vs. Office), but varies somewhere in the workflow that I never got. May I offer some recommendation to alternatives? My current go-to photo-editing software is Affinity Photo that nearly achieves professional functionality rivaling Photoshop. It's commercial, though, costs ~$50 (no subscription). It originally was a Mac program, but is now out for Windows, too. There's a free trial. It can use a great deal of Photoshop accessories (plug-ins, filters, brushes etc.), and reads and writes PSD files. It won't help you if you don't understands layers, though. In fact, it pretty much is layers galore. Everything you do is stuffed into a layer -- even brightness and color changes. Which is pretty amazing stuff once you understand it, but introduces some steep learning curve.