When introducing a new Sunday school lesson or a new group of kids, start the session off with a good icebreaker game that will get them thinking about the lesson topic. Print off pictures that go along with the lesson. These pictures should be fairly small, and they should be printed on thick paper, like card stock.
Hide several pictures around your classroom before the children arrive. Keep them partially visible, but not so obvious that he children notice them the instant they walk in the room. Once the children have all arrived, tell them the main topic of the lesson. Then, send them on a treasure hunt to find the pictures. Let them know the exact number of pictures in the room, and have them work together to find them. Then, use the pictures to teach your lesson.
Variations:
If you need the game to be a competition, have it be a race to see who can find the most pictures first. However, if your class encompasses a bunch of grades, this is not a good idea, because the younger ones may be discouraged. You could try pairing a younger student with an older student to make teams. You could also limit each child to finding a set number of pictures, so everyone has a chance.