Right now, it's pretty bland, and doesn't really fit in with the official style. The pose is a little boring too. Wouldn't a cobra/snake pokemon have a move coiled tail? The one you've got is too straight to look natural. As a pointer, always compare your sprites to official ones while working, in this case, Ekans and Arbok, to make sure you're on the right track and to avoid having to redo all of the sprite.
(Ekans and Arbok from Platinum)
Honestly, I can't really tell what this pokemon is based off. What you have now seems to be a frog/lizard mix with sand flowing out of it. I cant really offer any tips on this one because of its vagueness, but I advise you to fix the anatomy and face structure to make whatever it is based on a little more recognizable. As for the sand, you might want to use Hippowdon as a reference picture.
(Hippowdon from Platinum)
Bunneh! Unfortunately, this guy's going to need a lot of work before fitting in with the official sprites. The most noticeable errors you've got there are the bend of the ear, which looks unnatural, and the fact that it's going to topple down because of its disproportionate body. The eyes look hollow and unnatural too, as if someone had stuck two gems there. Buneary used as a reference would be helpful.
(Buneary from Diamond/Pearl and Platinum, respectively)
Um ... ? Loads of work needed since this looks very unrealistic. The most notable thing about it is how the shading doesn't reflect the possible bents and curves featured in hanging sheets. Also the color is too monotonous and the eyes follow the same method you used for the previous pokemon. For folds, you might want to check Duskull and Shuppet out, since they might offer guidance on that sort of thing.
(Shuppet from R/S/E and Platinum, Duskull from Platinum)
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Most importantly, your concepts need and basic outline are what need the most attention. I hope this post has helped you improved and I'd to see the results after they're finished. Keep working and you'll gradually improve!
