Another brick in the wall

"I have an old piece of wall outside my house on the street and it has a few bricks missing. For about two years now I have been putting in little objects such as small toys, pictures, odd bits of jewellery, sometimes models and bits of art and all other manner of strange objects. This has proved a delight to small children who sometimes take the stuff and even replace it with their own tack. Mothers and carers tell me they like it because it is a stop off point on the way to school or an excuse to get children out of the house in the morning. In short, it has become a children's cave of curiosities. I haven't been able to document this happening but i would like to mark its existence in some way. Any ideas?"