ECB penguin
Linux's mascot, encrypted with AES in ECB mode and still easy to recognise.
Encrypt a bitmap of Tux with AES in ECB mode and the result looks like the penguin under a layer of static. The reason is mundane. ECB encrypts each block on its own, so identical plaintext blocks become identical ciphertext blocks, and the large flat areas of the picture survive as large flat areas of noise.
It is the standard illustration in cryptography courses for one lesson: a strong cipher does not rescue a weak mode. Modes with chaining or a random starting value turn the same picture into something that looks like pure noise, which is the point.