Placemat - Pretty nice placeholder images.
RANDOM.ORG - RANDOM.ORG offers true random numbers to anyone on the Internet.
PlaceKitten - Dead-easy placeholder images. Of kittens.
Random Number Generator - Randomly generate integers or floating point numbers within a given range and specified discrete or continuous statistical probability distribution.
placeholder.pics - Lightest way to include placeholder images in your design
Random-Required - A random string generator that can take numbers, letters, symbols, Chinese characters and arbitrary...