Made with GIMP (
[link]):
How to make your own (any resolution)
step 0. Open the source tile of the image i made, get it here
[link]step 1. Filters>Map>Tile...
step 2. Enter desired dimensions, hit OK
stap 3. Export/Save the created image
step 4. Profit!

(Edit the image, tweak it, play around, make new art, ...)
P.S. For a nice wallpaper I recomend you just use source tile as tiled and voila, magic happens. Makes for a nice clean wallpaper.