K.W.
My mom always said keeping it around was the best form of birth control... :o) So... I kept mine around even after my hysterectomy. Just because. For sentimental reasons, and all of the reasons listed above. You have received some great answers. I hope they help.
If you want something crafty and opt not to keep the cribs... It may be cute to attach ribbons at different points on the rails with different shaped frames and wooden cut letters (for their names) and add pictures. I would do black and whites, with colored ribbons, but that is my own personal taste. You could even do large frames and distress the wood. It would look really pretty.