I refuse to say cute for a couple of reasons.
I'm not calling a picture of a 15 year old boy cute even if it is just a piece of art and also because I don't really find it to be all that cute. I think the better word to use, and this is just my opinion, is dull.
I use the word dull not only to explain the lack of said cuteness, but also because I have no clue what the emotion is. Have you ever knew somebody who had a hard time showing their emotions? I do and on top of being a good person to make fun of it's also a tad annoying when I have no clue if he's happy, sad, angry, joking around, or serious. This picture follows that theme.
The look on his face could mean several things and not being able to put your finger on it can be a tad bit annoying to the person viewing it. Is the character trying to be cute in some way? I hope not because it's a terrible way to position your face if you were. Is he scared of something and he's yelling, is he yelling to a good friend, or is he that kid in the chorus who's nervous so he stands up very stiff and sings quieter than the others. (It looks like the last one so far)
He could also be really surprised or frozen in fear. I think frozen in fear would be the look to go with here. So let's build off of it and see what we can do with this picture. Let's bring up that word dull again and use it in a different way. Can I suggest using it as another word for empty? I always stress this in my reviews. Would you rather see a piece of art with a character with no content around him or a character with a background? I think if you asked that to a general population that the majority would pick having a background.
A background could have showed the emotion on his face. You could have had him in a Christmas theme and we would have known that he was surprised or excited. Put him in a dark environment with shadows or some ghoul and we automatically know that he's scared or frozen in fear.
I think I can envision this piece being in a bedroom with the only light source in the room coming from a small glow outside of a window and the rest emitting from a door that is half way open. The light shines into the room, but is covered by a mysterious and scary shadow, which drapes over a portion of the light like a blanket.
Onto the character itself, the shading could have been a tad bit better, but I actually really like it. A lot of people don't put the time or effort into proper shading and shadowing. Even though I jokingly poked at your character by calling him dull and bland I do find it to be well done. The reflection in the eyes was pretty cool, the proportions makes him look very cartoony, and it's just a neat little guy all around.
Overall it's a nice piece that could really be cool with some extra content and feeling put behind it. Simple things like I suggested can make a piece of "art" into a piece of art quite quickly. Keep on working in your spare time and I'll be interested in what you come up with.
~ Review Request Club ~