Hello mholt.. I like this tree very much.. If I may.. In my opinion.. I probably would not do too much, if any carving.. I like the natural look of the tree and the bark.. It is simple, tranquil and looks untouched by human hands at this point.
Also, have you thought about swinging one of those branches down so it swoops down the trunk, so to speak. Either way, there seems to be many good options here..
Rob