Overlaps are one of the keys to volumetric success. Someday I hope to forcefully vomit all the information I've been spoonfed at school into a ginormous "tutorial" on how to draw volumetric things without shading. Naturally, won't really be a tutorial so much as a bunch of tricks that you won't learn just from reading about, but WILL learn faster if you know what they are and what to look for.
For now, overlaps explained with lines:
Fig 1 shows two ambiguous circles. Their position in space relative to each other is totally unclear.
Fig 2 shows two circles with a spatial relationship. The circle on the left is clearly in front of the circle on the right. Both figures, though, are flat.
Fig 3 shows two spheres overlapping and connected, making what appears to be a 3d shape. I strongly reccomend (To myself and to you) playing around with this lavalamp-like blob, try turning it in 3d space, stretching it, and changing the sizes of the two spherical blobs. Also play with cubes, prisms, triangles, rectangles, and any other basic 3d shapes you can think of! Most everything can be broken down into simple shapes. Your friend the wolf, here, is basically a sphere (not a circle!) for a head, an elongated cube or a cylinder (not a square!)for the snout-bits and a hacked-up bit of cone or cylinder for the ear. Because of that (the fact that most things can be drawn from basic shapes) practicing with overlapping triangles and cubes and stuff is grand practice for drawing pretty much everything!
The wolf, finally, shows some overlaps you could apply to your piece. The things that are closest overlap those that are further away, so the ear, in this position, would overlap the "Cranial mass" or main spherical-ish shape of the head. The Cranial mass would overlap the snout and neck, and the top jaw would overlap the bottom jaw.
So where, in your current edition, the head kind of flows into the wolf's left ear... make that an overlap instead! If I'm not mistaken, the ear is BEHIND the head, so have the "outline" of the head overlap the wolf's ear a few pixels. It'll make it look much more like a 3d shape and much less like a flat 'un. Apply the same general principle to your entire piece, and it should come out looking better. No promises, though
There! Overlaps explained!
On to the next bit.
I like perspective. Perspective itself is good, but trying to shift the perspective halfway through a piece prolly isn't gonna help as much as it will hurt, unless you're willing to start over entirely. Though I do agree that the perspective you've got now is more interesting, I think it requires much more working to get right, and you're prolly better off with the silhouette you had earlier.
Which leads me to my next point! You're straying from your original idea (I think?) and not, in my opinion, for the better! I quite liked the idea of the wolf silhouetted by the moon, but with every update you seem to be stepping more and more toward shading the thing "realistically".
Also, personally I say a big nay to having the eye there. It adds colours and stands out too much and doesn't really add expressiveness or emotion. Plus how you've got it now suggests it is incandescent and emitting light itself. Perhaps not that great, though laser-eye-wolves are pretty cool.
Last thing (Geez I post long posts) take closer looks at your reference. See how the hair on the wolf's back/lower neck kinda rumples and bunches? See how I emulated that in my edit? It'd probably help your wolf feel more natural if you did the same. Another thing to look at is the relative lengths of the fur. The fur on the top of the wolf's head does have some length to it, it does "break the contour" of the wolf's head. Compare the top of the wolf's head in my edit to the top of your wolf's head. See how the fur sticks out of the basic shape? Without that bit of fur breaking the contour, it wouldn't look like fur. You could shade the whole thing in realistic lighting with 6,000 colours, and simply because the top of his head is smooth, it wouldn't look like fur.
K I'm done.