I finally had a lucky break when touring the stock photo sites. I did a search for watercolors, and I ran across this Polish woman whose work dropped my jaw. Not only did she do these absolutely gorgeous watercolors, but she did enough similar ones that I could form a coherent series out of them. I got these images at stock photo prices.
Once I dropped them into Inkscape, the rest came naturally, except for the collection's cover, which took more fiddling.
Don't drool too much.
While I was at it, I changed the series from Jura City to Dwarf Shamaness, as Dwarf Shamaness is far more evocative of the content.
Even if I don't make money (it's a low bar, but I may just succeed), I don't see making covers for these books again. If they sell, wonderful. If not, those pigs aren't getting any more lipstick, and I just have to accept that I wrote wonderful books that just don't fit into today's market.