Most of this is based on the playful wolf. ;o So...
Your anatomy's fine in most places, but there are a few little wonky things about it. The tail and eye, for instance; the tail is too wide at its base, and the eye is positioned really, really weirdy. In fact, most of your animal eyes are too high, and tilted forward when they shouldn't be. Usually, the inner corner of the eye should be pointing just about directly toward the nose, when looking from a side view.
I'd say your toes could use some work too. The paw pads shouldn't be visible, since normally they'd be hidden by its fur, and the wolf is even standing in gra-ss, which should cover parts of the feet. They also look quite uneven, and shouldn't all get smaller the farther away they are. Toes aren't really on a big enough scale to warrant the use of perspective's whole 'distance = smaller' thing. It would be better to use the actual size differences in them, with the middle toe being biggest, the third toe being just barely smaller than it, the innermost toe being slightly smaller than that, and the outermost toe being smallest. Like you had on the hind left foot.
Your lines could definitely use some smoothing. Try using long, somewhat quick strokes, rather than short, repeated ones. Short strokes tend to look fuzzy and uncertain, but long ones, while they may require some cleaning up toward their ends where they'll get a bit more curly, stay mostly smooth.
And I'd suggest perhaps staying away from Photoshop brushes, like I notice you did with a lot of your backgrounds. Using a brush won't improve your skills as much as really learning to draw that thing will be, and doing things yourself usually looks better. Especially with clouds. Having a bunch of identical clouds looks really weirdy.
... My brain, all Earth Scienced up as it is, can hardly even fit around the fact that you have both cirrus and what seem to be altostratus clouds below a cumulus cloud. Or at least, I think it's cumulus. x3 Looks funny.