J.,
I had the same "wonder what to get" for a friend of mine who just turned 50. Someone gave me the greatest idea and everyone there loved it. So did I because it's thoughtful, personal, and inexpensive.
Michaels sells a frame that comes with a wide white matting, the glass, and a pen. The mat has an opening for an 8x10 picture to be added later. It was only about $20.00 or so. I bought a package of the thin tip sharpies also.
I left the glass under my bed to make sure nothing happened to it. I set the frame up on an easel with the pens and signed my message. I walked around making sure to tell others to sign. I had a waiter take a few pictures of the whole group. The next day I had the chosen photo blown up to 8x10 at Meijers, put the picture and glass back in and took it to my girlfriend.
It was soo nice, even I was impressed. Now sshhhh, don't tell my secret, lol. I plan on giving this gift often. What a great memory.
Good Luck,
L.