Ok, not exactlllllyyyyyy a party theme, but Frosted none-the-less! I love the idea of doing special messages to your loved ones! I remember as a kid getting little paper notes from my mom in my lunch bag sometimes...
... here are a few cool ways to Frost your next message!
Source, cookie letter stamps
Source and tutorial
You know those magnetic words that you can make messages out of? Why not do it in cookies! You could make a great message and put it in a decorated box, let someone figure out the message, then eat it! lol make sure to use edible markers! Source and tutorial