Hey Ron, sounds like you've got it made! I love cherry and walnut.
As for thickness's of the woods you'll need, I haven't done any bowels so I can't help you there.
For lettering depending on size you will need 1/4", 1/2" and 3/4".
For ornaments you will need 1/8" and 1/4".
For names I would use 3/4".
As for portraits, I would not use hardwoods. I would stay with a high quality plywood like Baltic birch.
Make sure that barn wood is dry. It needs to be in the 8 to 12% moisture range or things will crack when it does dry. So be careful.