3 variants for a Gimp splash screen.
Copy to ~/home/your-account/.gimp-2.6/splashes
Create this directory if it doesn't exist. If everything works fine, the images in this folder will be displayed randomly each time gimp loads.
I will provide the xcf file to download later when I'll be not so lazy to find a download location.
The simplest one is obviously inspired by photoshop splash screen.
On the two other ones, the little thingy in the middle is a vector downloaded from http://vector4free.com/vectors/id/103