I want to point you to some posts with great bark photos:
Lucinda from the UK with her Hawthorne
Marqueta from Idaho in the US with her Osage Orange
Amber in Ottawa with some very nice bark close-ups 1 & 2
Jen in New England with the fallen Birch
Annette in Florida with the bark of her Jacaranda and its great seeds
And Mark on the Pacific West Coast has a nice post on moss.