A real cool tattoo here.
It is the crest/symbol/emblem of some kind of old/ancient warrior. It features a dragon looking creature as an outline to the rope-like border outside ot the middle.
While in the middle of it, it has a knight riding of his horse with his sword and shield at his side. The shading of the horse is pretty good and there are many small details put into this tattoo that makes it recognizable as an awesome tattoo.
The shape of this tattoo fits perfectly on the spot of this mans arm.