The info below should be of help. Be sure to follow the link in the last sentence that says, 'For more information....'

Here is a link that might be useful: concrete

There a million different treatments for the wall. Almost anything you desire. Brick, rock, stucco, paint, vines etc. Anything you do is only going to be as good as the attachment.. For Instance if you go with the stucco the wall should first be roughened so the stucco will adhere. or could be lathed. With brick or rock wall ties should be used. For paint or anything else that will be glued, like a veneer brick or rock, the wall should first be washed with dilute muriatic acid. When you deside what you want then do an internet search and learn how to do it properly.