I'm taking my first real shot at game development, and seeing as I'm doing it as a self-enrichment and creative hobby, more so than seeking to get a concrete project out in any reasonable amount of time, I'm taking this opportunity to dip my toe into the visual arts for the first time... essentially ever.

I've never really had an eye for art, and I'm looking to learn. With some guidance from tutorials and friends, I've made a basic character sprite, and would like some feedback and constructive criticism before I try and animate the character.

For the sake of context, I've gone ahead and stuck the character in a test room of the game which, it bears mentioning, has graphics in an extremely placeholder state.

Any feedback you can provide, be it for proportions, shading, general pixel art issues, or anything else, is extremely appreciated!

Hello, first let me say welcome to GameDev. 

Observations about your art:
at first glance I didn't grasp dimensional structure the stage/platform your avatar was standing on until analysing it further.  Granted it didn't take me long to figure out what was going on ( what the stairs were and where the lower and upper levels were ).  But given the orientation of the view you chose, I'd say make it easier to allow users to grasp the structure from the corner of their eye.  This way they don't have to inspect individual elements to make sense of the scene.  For instance, your selected frame of reference doesn't allow for shadows ( albeit small shadow sampling from your avatar ).  But shadows do allow for at a glance conceptualising.  I don't know.  maybe I'm over complicating things, but I think you should play with it more.  

Thanks for the welcome and for your feedback!

Sorry if that was a little unclear, but that room is very much a terrible placeholder and absolutely not intended for any kind of feedback. The character sprite is what I'm looking for advice on.

(I'm planning to have the light source be from the right and front, so objects will be casting shadows to the rear left, which will give a much better frame of reference. I may also cheat the view à la Link to the Past in order to show some of the side of the platforms.) Please disregard the appearance of the world for now, I was simply trying to put the character in some form of context.

I've updated the sprite a bunch since this was posted. I need to tweak the shoulders on all of them, and the jawline on the middle one, but any further advice on the character would be greatly appreciated.

I'd say it looks pretty good, depending on what style you are going for, in terms of overall pixel art technical stuff and proportions. You could always image search "pixel art faces" and see if there's anything you could adapt. Maybe add some more shadows for the nose? I would also add some more detail to his clothes, maybe something on his shirt, or an asymmetrical patch on his pants, or a stripe on his socks. Is he supposed to be super clean cut? Slightly rebellious? Blank slate?

One thing that might be helpful is increasing the contrast. Right now he's relatively washed out, and you definitely want your player's character to stick out. Note that also depends on what your backgrounds will look like. The safe and/or lazy way to guarantee contrast is a black outline on character sprites, but that doesn't seem to fit the style you are going for.

Here is and example of what I would do (but you know what you're going for better than me):