I was actually confused. Turns out I downloaded themes for "USB Loader GX." Ok, so now I downloaded themes from Configurable USB Loader. And those work alright, but I have a new problem.
How do I get the games to display all across in 3D boxes? Right now it has two rows of 2D boxes: three at the top and two at the bottom. I tried to edit the config in configurable USB loader to not use rows, and to display as 3D, but the changes didn't take. So I edited the config manually in notepad and then confirmed it in the configurator, and the changes DID take. But they didn't show up on the USB Loader program itself in the Wii. It's still displaying as two rows of 2D boxes.
This is what I'm trying to make it do. And I got this theme from
here. It's in the Configurable USB Loader section.