Tattoo question?

I'm wanting to get a tattoo for my son...and future children. I've been thinking about getting my son's handprint, that way later on I can get my other children's handprints also. However, handprints and footprints are common. Does anyone have any idea of what I could get? I dont want to get a picture of him because if we end up having 2 or 3 more kids, I wont have enough room to get all of their pictures on me. Any ideas?