I have nothing to do, so here goes...
First of all, interesting idea. It's just... nice. I'm not quite sure why I like the pose, but I do :D
There is almost no contrast in the shading however. The entire face is nearly the same shade of gray, making it look as if you had cut out a shape in gray paper and pasted it onto the sheet. The edges of shapes, for example where the jaw meets the neck, are a perfect transition from one shade to another. In reality light bounces off curved areas, creating a slight highlight around the edge, or sometimes a shadow. The shading on the hand/sleeve is very nice, though the thick lines around the fingers are unnecessary.
I like the texture of the hair right above the magnifying glass, but the hair to the right, left, and above of that patch is very rough and un-hair-like. The dark spot at the top of the head is seems to be the result of you trying to show that it is darker than the rest of the hair (well duh,) but it is overdone, especially with the low contrast in the rest of the piece.
The eyes are incredibly shiny. It's a nice effect in cartoons, but in here it makes the eyes look glassy and fake. The right eye seems to be missing some eyelashes, and The eyelashes in the left eye are pointing in unnatural directions. If you look at your own eyes in the mirror, you can see that they're a lot thinner and there's more of them. I think it's already been mentioned, but the left eye has tons more eyeliner than the right. I'm guessing you meant for it to be that way?
The right eyebrow is very easy to miss. Again with the contrast. There is something above the left eye that I don't recognize.
The magnifying glass has no shading whatsoever. It looks... kinda weird.
It would be helpful if you had included a reference photo, because as it is now I can't tell you anything specific about the shapes themselves. But you're probably already tired of reading my post, lol.
Basically, don't be afraid to press down hard on the shadows. Shade exactly what you see, even if it seems that it would look weird. It won't in the end.
Keep on drawing and improving! <3
May I ask what you consider to be a long time?
I'm seriously not believing you did that in #2 pencil and a Crayola colored pencil. I don't want to say that there is no way, but I do not see the effects being that good with them. If you did, wow. But I do not see how you did many things with that limited of options. There are some things that they alone cannot do. And in my opinion this is one of them.
But wow, kudos on this and what you used. Literally insane.
Crayola isn't that terrible, lol. You want crap, use Roseart.