I knew that Justin Bieber was a forlorn metrosexual humanoid. It all makes sense now...I'm sorry I had to because the guy in your painting looks like JB. :P
Anyways, you drew the face pretty well. There are a few issues with it, though. The line that makes the right side of the bridge of his nose is poorly drawn and doesn't really blend in with his face. I think that's because you drew the line a little too long. Also, the crease above his lips is too darkly colored, if you ask me. Next, his hair would look better if he didn't have that one piece of hair sticking out. Lastly, he doesn't have a columella, so there's no skin between his nostrils. I know you said in the Author's Comments that you wanted to give him unusual characteristics, but him not having a columella looks really unappealing.
Besides the guy in the painting, I like the colors you used. The colors make kind of an eerie mood. The tone of his skin goes well with the background, too.
I'd say this painting is a little more than mediocre. You have a few things that should be fixed.
P.S. If we weren't friends, I would've probably given you a zero because he looks like Justin Bieber. lol jk