Endless Rain Poster:Nightstone

Hello! I'm dropping in from #SeriousArtists for some critique!

I'll start with anatomy! Overall, the anatomy of the figures is good and coherent. The proportions are about right, though if you're going for more human-like anatomy, the characters are a bit slim/tall for humans. Just mentioning that in case they're meant to share the same proportions as humans rather than just naturally being a taller or more slender species. I think as far as poses and anatomy are concerned, the green character on the left is the 'weakest' of the bunch...! The pose is a bit unnatural and it looks like the arms might be a bit too long. Drawing people from life or photos will help you get a better feel for poses and overall human anatomy! C:
You can try gesture drawing too, where you try to quickly capture the pose a figure is in. Here's an interesting tool which generates a slideshow of photographs to draw from, where you set the length of time each photo shows, start it up, and start scribbling away on paper, trying to capture the pose of each photo.

As for lighting, it seems like the light source is consistent so I can tell it's coming from the top left and all the characters are shaded to reflect that - which is good! (The white one might be a bit of an exception though, where it looks like his chest is being shaded more brightly than his arm, making it look like light is pointing at him from the viewer's perspective.) With light and shadow though, a shadow is actually darker where it begins/is closest to the lit part of the object. So it goes from light, to dark, to slightly-less-dark. Here's an example of a sphere to show what I mean: [link]
It gets less dark after the start of the shadow because light is reflected off other objects and back at the sphere. Keeping this in mind when shading your characters will help them appear more three dimensional! C:

Aaaaand, I don't tend to feel confident commenting on composition, but I'll try anyway since I feel like the composition might be a bit 'off balance' with the two large objects in the top left area of the image, like maybe there should also be something large in the lower right, or the positions of large and small objects should be switched up a bit. This page talks a bit about distribution and balance and has some little example images of how the size and positions of objects can look good and bad: [link]

So yes! I hope what I've said can be of help to you! Keep up the good work and good luck with future art!