I learned about the general premise of making my own dual-screen wallpapers from videojug. Below are some wallpapers I use on a regular basis. I use Photoshop or GIMP and the source file is set to 300dpi. That way I can resize images without losing quality. The final product is reduced to 72dpi. You can leave it at 300dpi if you want. I did that so I can share the files easier.