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I find this theory very interesting.. in short, here:

A recent study published in BioMed Central's open-access journal, BMC Research Notes, suggests that people most appreciate a piece of music containing certain specific patterns that sound complex, but are actually easily simplified and stored by the brain . This "information compression," said study author Nicholas Hudson, a biologist at the Australian Commonwealth Scientific and Industrial Research Organization, is similar to how music compression software reduces the size of audio files by identifying patterns and removing unnecessary and redundant data.

http://www.livescience.com/33050-what-makes-music-enjoyable.html

Scientific paper backing it:
http://www.biomedcentral.com/content/pdf/1756-0500-4-9.pdf

That is an interesting question. A solid colour image is very compressible (~0 bits/pixel) while an image made of random static is not more visually interesting but is essentially incompressible (24 bits/pixel for a 24 bit colour map). It would be interesting to measure the bits/pixel in the rated images of the FF archive.