wall sticker christmas

My boyfriend plays tennis, so he's always going away to tournaments. Since before we started dating, I've written him good luck notes, and he always takes them with him while he's playing, then puts them on his wall when he's not. I want to do something more creative than this every other week, but I'm running out of ideas. There was one point where he wanted to quit because it was getting the best of him, so I wrote on a tennis ball, "Don't give up; accept it as a challenge." And he loved it. He carried it with him all day before he left, which was funny.
I went to the craft store yesterday and bought some scrapbook pages and some tennis sticker stuff to make a big good luck note, but he can't really take it with him. this week, since it's halloween, i made him a cute little gift bag because he's going to be driving instead of celebrating. and it's also our 2 months.
Also, I need ideas for a good Christmas present for an 18-year-old guy.