I have decided that for each one of my two kids' birthday parties until age 5, I will make a T-shirt that has some type of picture that goes along with the theme of their party.  They wear the T-shirt for the length of the party and when it starts to come to an end, I have them change t-shirts, the one made goes on a board, where I have each child invited to the party sign their name with fabric pins.  My son (3) loves to wear his T-shirt all year round and likes showing it off to family, friends, and even strangers.  Example: My son's 2nd b-day had a choo-choo train theme. He and I dipped train sponges into red, blue, and green paints and stamped one of each color onto a white T-shirt and wrote "Choo-choo I'm 2!" in puffy paint. All the kids had fun signing!      Another idea: For the 1st b-day, I made a "Happy 1st B-day (name)" banner and hung it on the garage door for decoration (my kids' parties are outside) as the party ends, before kids leave I have them dip one hand in (a choice of 3 colors) finger paint and have them place their print on the banner and then sign their name next to their print.  It makes a sweet momento for years to come! The kids enjoyed it and so did I!