These are a few of my experiments using SVG files for background images. While I designed these at a size of 1600 x 1200 pixels, that was mainly to get the proportions right. The images themselves are resolution independent. Also, the actual background colors are for example only - the image backgrounds are transparent. This means that you can set the SVG image as the backround image, and then change the color or gradient to whatever you'd like! The logo will stay the same, and the semi-transparent drop shadow will take on whatever color is behind it. Try them out!
Your web browser can't display these files. To use them on your Ubuntu/Gnome desktop, right-click on a thumbnail and select "save link as". Once saved on your hard drive you can right-click on the desktop, select "change desktop background", and use the add button to add the graphic to the list.
This is obviously NOT my handiwork (except for the logo in the corner). Some people think logos on wallpapers are bad. I happen to disagree. I've added this for the other oddballs among us.