A Gift To God (but where to put it?)

My 5 year old son is an artist in the making. Talent or not (still too early to tell), he sure likes to draw but even more to write. Lately, he has been making signs with slogans on them about his love for God. All of that has been fine and quite interesting to my wife and me. Today though, he started saying that he wants to give these signs to God. Like a gift. Like putting them somewhere for God to read.

I'm all for alternative and new expressions of our love and faith and devotion to God. I love it for myself and am now learning to facilitate it for my son. This is new to me though. How can we do this? He likes hanging them up on the wall but now he folds them up and wants to have a special place to put them. He has a tithe jar that he puts his tithe into whenever he receives money from a birthday or a job around the house. For now, we're putting them in there but the volume of banners and signs are quickly outgrowing the quart jar he has for his tithe money.

Any ideas? We so want to encourage this form of expression in him. Graffiti on the walls is one way but we're moving in two weeks so it will all have to come down and be cleaned up. How to let a 5 year old, intent on letting his light shine through this outlet, do just that???