I know you wanted something a little more "outside the box" than a note in the lunch box but I still do this and it is fun! Instead of the usual "Mommy loves you" note I started putting funny pictures of animals etc. (you can find so many on the Internet) and then when they could read a "Joke for the day". My boys said their friends still want to know the "Joke for the day". It helps break the ice when making new friends to show a goofy thing your mom did.
I still try to make a fuss of them when I pick them up...sometimes I have a balloon or a plate full of cookies they can quickly pass out to friends. During the hot months, I bring a popsicle to have while we walk home...
If one of my kids is worried about a test that day I send "open before" and "open after" notes of encouragement. For my older kids I sneek in their folders and grafetti on one, a funny drawing and a note of love. I do it in a strange place and it takes them a while to discover it.
We also have a "red plate" at my house and when you have done something great at school you get to eat off the red plate at dinner.
I also give out "holiday pencils" at breakfast, they have them for just about every holiday and it is fun to get a silly new one to take to school that day.
Kids love anything that makes them feel special and loved and is a fun conversation starter to show their friends!