Well... ok, just image quilting for now. :)
Image quilting was described by Effros and Freeman in a 2001 paper that you can find on this page.
Basically, starting with a small image, you can quilt samples of it together in a clever way such as to create a large image that does not appear to be made from tiles or even from repeated sections of a small image. For example, starting with this image of gravel:
We can generate this image:
More examples...
source image:
result:
source image:
result:
