ChopSuey is a project mainly written in Python, based on the GPL-3.0 license.
A utility for cutting up images for wallpaper on multiple displays
ChopSuey, Copyright 2010 Peter Hajas
Run with "python ChopSuey.py pathToYourImageFile.jpg/png/tiff/gif/bmp/bitmapsaregross"
ChopSuey is an awesome command line tool for people with lots of displays that might not match up perfectly. If you'd like to generate beautiful wallpapers from large format images, ChopSuey is the tool for you. Please see the LICENSE file for copying rights. If you use this utility, I'd love to hear from you! Contact me at peterhajas (at) gmail (dot) com. If you can, I'd also love to see some images of your configuration.
If you're looking for good high-resolution wallpapers, I recommend NASA Hubble images.