I have a picture of my son somewhere that makes me laugh whenever I come across it.
He was about 13 months at the time, and wearing nothing but a tea towel around his waist. The towel wouldn't stay so he's hunched over, trying to hold it up and run at the same time. His tiny butt is pointed at the camera and it's a motion shot, you can tell that he's about to ditch the towel...
As is, here's another of him (butt crack unseen) during a family fingerpaint session that also makes me smile.

Can you look at a joyful smile like that and NOT smile back?

ETA: Wrong painting image