Lets see.. If I were to give this critique, I'd suggest two things.
One- that there needs to be more progression of the tones in this picture. I can see that it's not meant to be high intensity light as his face isn't heavily shadowed- it's just dark. I think that if you lighten the background, or atleast the ceiling, it'll make him pop from the page alot more cause you'll see where he finishes, and the background begins. You can see this easily if you turn the picture grey scale- you'll notice little difference in the over all tone of the picture.
Two- your brightest value in this picture is the broach- I assume this isn't the subject of the picture? The next value after that is a tie between the sword and the background. I assume neither of those are the subject either? If they are the subject, then they're fine, but if they aren't, I subject knocking them back because they're the first things my eye sees. I feel my eyes darting about the picture cause of it, rather than examining it. I found that if I pretended they weren't there, then the man became the subject of the picture finally He was very dark, but the subject nether-less. I hoped those pointers helped you. IT's a lovely picture, and I think with those tweaks it'll bring the most out of it :)
He has quite a presence - he seems very self-assured, and almost serene. And I love the metallic surface of his sword hilt, and the deep shine and shadow of the jewel on his shoulder - almost an inner glow.
Maybe build up some more highlights in the clothes, or differentiate the edges more sharply, or both? As is stands he seems to fade into the shadows of his castle a great deal.