I have a little shelf I attached to my wall, and on it are a couple candles. Both are large ones, and just sit on their holders, not in them. The wicks themselves are about five inches from the wall. Is this far enough away to ensure no accidental fire will happen? Obviously, I’m not going to leave them burning if I’m not around, but I don’t want to go to the kitchen for two minutes and come back to see my wall ablaze.
If you keep the wicks trimmed, and no other flammables such as curtains are within a foot or so of the candle, you should be OK. I’m more conservative, with candles in glass containers, a foot+ from any other combustible surface. Setting stuff on fire would be very bad on my CV. 
Related thread:
Heat From Candles
You should be OK, but in the old days candles near walls were kept in sconces. Why not play it safe and put a decorative, reflective, and heat diffusing sheet of metal between the flame and the wall.
Also, don’t forget about soot. The closer to the wall the more problems you’ll have with soot collecting on the walls and ceiling.