Being perhaps the cutest thing to happen to web development since ever, placekitten.com allows you to create placeholder images just using a link with some set dimensions on it. Try it out: http://placekitten.com/g/680/200 (the /g/ makes it be in black and white, remove it for color images, and change the numbers for different sizes). I’m kind of in love.
Please continue to force me to build websites before you give me any content. Your site will be covered in kittens.