Choose a background!
The Open Clip Art Library gave me the pictures I used for the "Neat" backgrounds.
Practice your HTML5 here! Perhaps displaying obscene pictures would be nice?
Note that some browsers may allow sloppy HTML5. Sadly, scripts probably won't run.
I made the following pictures with MATLAB...
When MATLAB and image-editing software combine forces, the default background for this webpage results!
You can make your own colorful patterns using http://www.mathworks.com/matlabcentral/fileexchange/28205!