OK, I've been fooling around more with GIMP, and here's more or less what the front cover of Trang is going to look like now:
The text has an embossed look, thanks to GIMP's bevel tool--what I like about that is that it helps the text stand out from the background art. That allows me a freer hand with where I place things--before I had to be really careful because the text would just vanish into the artwork. The downside is that the Copperplate Gothic I was using before just doesn't bevel well, so it's gone.
Also you'll notice that my name is a lot larger now. Some would argue that my name should be larger than the book's title, but my title has five letters and my name has ten, so that's not going to happen with my limited design skills. But now you can read my name in the thumbnail, which is an improvement.