I discovered that it's easy to create unique, psychedelic desktop pictures using screen capture and the Jelly visualizer in iTunes. Below is one of these desktop pictures. Click on the image to see the full-sized 1680 x 1050 image (my computer's screen size).
I was looking for some abstract desktops with a black background because I find them easier on the eye and less distracting when I'm editing photos, but I couldn't find exactly what I wanted, so I decided to make my own with iTunes. I have an Apple computer (an iMac), but I would think that Windows PCs with iTunes could be used to make these as well, but the method will differ a bit.
To make desktop pictures like these using a Mac, first open iTunes and in the menu bar, choose View -> Visualizer -> Jelly. The Jelly visualizer works the best for this. Next begin playing a song and either press the command T keys or in the menu bar choose View -> Show Visualizer. Wait a few moments for the song info shown in the corner of the screen to disappear, and then press the command shift 3 keys to take a screen capture of the visualizer. I just kept my fingers on the command and shift keys and then repeatedly pressed the 3 key to take multiple screen captures. When you are done, press the esc key to exit the visualizer. Take plenty of screen captures because some of these won't turn out. The captured images should show up on your desktop.
Below are some of my favorite iTunes Jelly visualizer screen captures. Different types of songs produce very different visualizer images, and most of these were captured while iTunes was playing Aquarium by Camille Saint-Saëns. Click on the images to view the full-sized 1680 x 1050 versions.