You can still display your treasures, but perhaps not so many on every available space -- just a few like things in a few places). Or you could keep them in one room (bedroom, craft room or guest room).

I like the idea of a hutch or bookcase with glass doors. You can display your collections (in an organized fashion), and he can have the door closed to prevent a "random knickknack" look! Just make sure the items aren't all crammed in for the sake of having them ALL out. It would look nice to have them arranged as sort of a gallery - mixing books in with knickknacks and so on...

If you have a ton of these knickknacks you could always have more than one bookcase, or rotate the items out to keep it fresh!

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I just got a new decorating book - Better Homes and Gardens (not sure which edition, probably the newest) - and it has a pic of this white bookcase with a wallpapered back, which I love! Wish I had the image on my computer to post.