placeholder.pics - Lightest way to include placeholder images in your design
QuizUp - QuizUp gives you the opportunity to test your trivia skills against friends and strangers throughout the world.
PlaceKitten - Dead-easy placeholder images. Of kittens.
A Google a Day - Online trivia game where you use Google's search to answer questions as fast as you can.
Fill Murray - Custom-sized placeholder images of Bill Murray
Trivia Crack Kingdoms - The amazing quiz game that lets you test your knowledge and challenge your friends to see who is the smartest. Developed by Etermax