This one may not look too good, but it is my first try at this effect. Better ones coming soon. (It took me around an hour to perfect this one).
To make this,
1.Open an image that has lots of dark and light areas. I used this:
2.Apply Filter>Blur>Gaussian Blur, with setting of 75px. (yes, a lot!)
3.Go to Layer>New Adjustment Layer>Color Balance.
4.Play around with settings to get something that is dark in the area you want the ribbons in. It takes some practice, as there are 9 settings to apply.
Actually, forget it… I will post a tutorial with a similar but a better image, as I don’t even have the step-by-step images for this one. Just enjoy the wallpaper till then!! Here is another image to satisfy your primal wallpaper needs.
p.s. If you want the first image without the windows logo, just ask..