Using a large number of images from your database to create a desired output. It is essentially a matching problem where you find the image which most closely matches the pixel in your desired image. The original image is 4988x5025 and used a thousand images as source.

I did some minor tinting of source images to increase the match which some people consider cheating. Note that I did not superimpose a low frequency version of the klimt image which is a total cheat. Reach out to me if you want to see the original or if you want help in how to do it yourself.