A web based paint program using CSS3, HTML5 Canvas and javascript was used to create this image in Google Chrome 6.
My text started out hard to read against this background. I was able to brighten the image with a standard image editor, not Gimp, which is too hard to use for simple tasks. I remember a Windows program, Lview in which such tasks were much more straightforward. This still doesn't meet the objective to do the background entirely with SVG or CSS directives. The PHG file is still a quarter megabyte in size. I could easily create a JPG that should be much smaller, but possibly I could convert the PNG to SVG, that would be nice, since I already know that SVG is tiny and can be used as a background.
The conversion of the PNG to JPG cut the image size down to 40 KB, but Gimp 2.6 said that it lost transparancy, which must have been the problem with the wild grapes backgrounds I tried a couple of week ago. A background color would fill all of the white, really transparent, areas of a SVG or PNG background, but not a JPG. Gimp did not have a convert to SVG option, maybe the resulting XML would be complex and the file would still be as big as the JPG or larger, but it would have tranparency. Possibly a simpler design with circles and ellipses in the nice pastels shown here would done with Inkscape be a good compromise for size and effect, if I wanted to use transparancy with a background color. For now, what I've got is adequate.
Inkscape is not very intuitive, you can think that you are creating objects that don't appear since they aren't filled with color. I find it harder to use than it should be, same with Gimp. It seems programmers get caught up with the implemention and forget to see if it is actually usable by users who don't understand the implementation and often don't care.