This is a hundreds chart hidden picture. I call them fundreds charts. The hidden picture says YOU ROCK and uses base ten clues. That means that the clue is illustrated in base ten, place value, and they have to count the blocks or count their tens and ones and color the number according to the code on the clue.
I print and cut out all the squares, laminate them and then post them around the room so the kids can walk around and do the activity.
This would be great as a center activity, whole class or waiting activity.