Decorating this wall is a work in progress, but I love how my shelves out of trim pieces turned out. Total cost was about $25 for all three shelves. The picture below shows how 3 pieces of trim (plus the corners) make one shelf. Its easier to make the whole shelf before mounting it onto the wall, then caulk and paint, just like any other trim. The corners are cut exactly like you would cut crown molding (the angle is hard to get, this is the hardest part). Picture tells a thousand words:
I painted them Swiss Coffee to match the rest of the trim in my house. The whole thing:
All three:
Completely Type A 
how do you nail the bottom piece to the crown molding?pam
It’s the trickiest part, that’s for sure. You want to get the top piece on also, then the middle piece sits at an angle between the two just like if it was in the corner of your ceiling.