I recently stumbled across a great website with a lot of tutorials for Gimp, Photoshop and other programs. I found a tutorial named "Easy way to create light effects in Gimp" made by a 14 year old from Germany! I tried the tutorial and the result was great and it as a wallpaper looks pretty good.
So here it is, the result of the tutorial with minor changes in the process due to the higher resolution I choose to do it on.
As usual I also attached the Gimp XCF file I used to make the wallpaper. In this case I have also attached the PNG version of the wallpaper which had a size larger than allowed for the content file.
Reader Tutorial: Easy Way to Create Light Effects in GIMP in 9 Steps: