I request some critique for my recent work.
This is one of my first yiff stuff; say i'm kinda ruined. I really need some advice on their expression and genitals

http://i.imgur.com/c2pmzxy.png

Remember less is more with expressions, imho that rabbit looks like those creepy ass department store mannequins.
I'm not an expert on rabbit penises, but I'm guessing you went for some sorta anatomically correct bunny boner, and it looks fine.
The horsecock is fine as well.

the biggest problem is their faces, they are really wonky. for the horse i suggest looking at photos of real horses and how their face looks like from that angle and for the bunny i suggest using human face anatomy as base or maybe cat heads. also their overall head size is a little bit too small, largen their heads but keep the muzzle size same

I personally like the faces and the head shape, but they could be a little bigger. Other than that, everything else is pretty good

Overall, it looks pretty good. Others have made pretty good points on ways to improve it further. I kinda like the horse's expression though, has some personality in a cartoon sort of way. If you wanted it a bit more realistic though, you'll need to have a stronger handle on the face shape. Mutisija's suggestion was a good one.

One thing though: the bunny's arm which goes behind the horse's head/neck looks like it'd be an almost painful strain on the shoulder, especially since it's forced to go almost straight up in the air and is therefore unable to help support any of the bunny's weight without putting a huge strain on his shoulder socket. If his shoulder were somehow back or up a little bit farther, it might leave room for the arm to take a more natural angle/position around the horse's shoulders.

Also, if his arm's going back like that, his shoulder would actually move up a little bit, no longer being level with the shoulder that has the arm going down. If you look at real life pictures of guys stretching (without any clothes to get in the way of seeing what the shoulder lines and muscles are doing) you can see how having the arm going up like that would change where his shoulder is at visually in relation to his other shoulder and torso. Other than that, it looks pretty good for a sketch. Just some refinement of the finer points on the anatomy in a few key places. Otherwise, it looks good.

Thanks for help, I did something with them
http://www.furaffinity.net/view/13920861/

I don't even know how is this pose even possible in real life, and I could not find any somilar here (yet).
The bunny's face still creepy - can anyones show me a proper 'cum' face?
Edit: I found one https://e621.net/post/show/383366

Also I'm thinking of commissions in the future; what do you think?