Well, yeah... that looks pretty real... something that could exist in real life.

Have a harder time imagining four legged things

It wouldn't be so bad for something not standing upright, although it would be easier to add lower arms, than extra legs, I'd say it's easier to fit onto a rib cage, than to fit an extra pelvis. But if your spine is long enough... :D

XD
was just thinking double-pelvis than "centaur"-style
Still can't let it go, how it'd work and whatnot.. >.<;

Depends a lot on how much you ignore realistic anatomy But they can look good if you pay a bit of attention to how it would look if such creatures did exist and keep the visual physiology straight.

Bear in mind though, I am a little biased in this dept

I LIKE realistic anatomy, it doesn't have to be perfect but part of me really thinks art looks better if the muscles look like they're pulling right. Some people seem to just attach stuff without actually giving it muscles to move, and it looks unnatural. Maybe I just like the upper pectoral-to-deltoid area :D

If you are interested, check out how some of the artists have depicted the musculature on the Vanguard aliens I get a lot of commissions of. That might give you some inspiration maybe?

I did, and no, that's with arms in front of each other?

Aye, a different take on how to handle 4.armed critters. Stacking the way you have it is probably more easy to manage in terms of getting the anatomy looking good.

Whenever I see these I always think of this one time when I was in grade three or four. Armfarts were really funny back then, though I got it wrong the first time and used a fist instead of a cupped hand. It hurt a lot, and would probably hurt people like this pretty often. Though if the arm was just low enough then that wouldn't happen, and your anatomy looks like it might work...

Okay, so I guess I brought this up for nothing, your anatomy works fine, though the lower arms aren't able to move foreward and have very little lifting power. If they could move then the upper chest muscles would be weakened from the bones underneath being able to move around.

Well you are right in the arm farts part, they'll definitely have some odd armpits!

Hmm yes but I was thinking.. maybe not have a clavicle for the lower arm pair. Maybe their pecs can just grab into the ribs, there's more ribs where they are than at than the upper arms where the rib cage is starting to disappear. The scapula muscle stuff can probably layer just fine though, as long as the scapulae themselves don't bump into each other, that can't be pleasant.

The reason that the clavicle is there is for foreward and backward motion, but then there's the neck muscles and shoulder muscles which help with lifting, so all that these would be useful for would be typing and gesturing. Maybe scratching an itch, but only if it's within swivel distance. They could also be used for pushing though, pushing and pulling if the back muscles aren't affected. But lifting isn't a possibility, for that the top shoulder muscles need to be more developed and would have to connect under the upper armpit. This is assuming that the two sets of arm bones aren't connected, which wouldn't make sense if they were.

Honestly I think the anatomy is pretty dang good. .__. I faved this not only for the fact that It's awesome, <3 But also...I have been looking for some good four-armed anthros/humans. I have no idea how to properly set up the anatomy for something with four arms, and I've recently gotten myself into a bit of a situation, needing to draw some dragon characters with four arms. Hehe came to my rescue. xD I hope you don't mind if I look at this, and study the way you set it up for help with drawing my own four armed character? (actually its my bf's char but yeah >.>)

If you want to experiment with Really contemplating realistic anatomy, the thing to do here would be to sketch the skeletal structure of someone like this.
I admit I am a fan of Multi-arms myself. Mostly because Im a fan of Armpits ;)

But in truth if you looked at a sapient with four arms, more then likely it would have evolved in a way where it isn't simply one set of arms "doubled" but more then like two different sets of arms. A 'primary' set of arms, and then secondary. the lower set would probably be smaller and slender, evolving for manipulating things, while the upper-set would evolve into heavy lifting and more brute force.

You should try doing a profile of this character from head on doing flesh and then skeletal.

The multi-arm anatomy is very well executed! You should try 6!!

I just heard of you recently. And yes, you can make realistic, logical multilimbed characters. I do that myself.