Revamps look great. on surface view, i don't see anything wrong with them. Nice job, btw, on the leaves.
Now, your project sprites seem to have the right idea with the shading and the outlining, but the anatomy is just a bit too blocky for my preference.
Thordog and badylug may need some shading near the legs. This shading isn't for diffusing light/dark spots made by shading, but instead, for giving the body and anatomy more structure. This technique is called chiaroscuro. What it does it make the sprite look more "3D". By adding a line of a darker tone, it makes an extension of the legs. In that respect, it pretty much makes it so the sprite doesn't have four little stubs coming out of his belly.
As for the shading, it's pretty much on track, but it's a bit rigid, such as on the snail evo's shell, or on flartle. When the anatomy is round, you want to make the shading more rounded as well.
Overall, your sprites are not bad at all. They have some work needed, but they are getting there.
I would rate thorndog a 5/10. He needs more definition for his legs. The same can be said for badylug, it needs more leg defintion, but it's eyes are also a bit strange. So i give badylug a 4/10.
Flartle gets a 6/10. His shading is good, but there needs to be more of a roundness on the shell, and the head is a bit too light overall.
Slug gets a 7/10. It's a bit cylindrical, but is a good sprite overall. You could maybe improve this sprite by lightenting the outline of the yellow to a more brownish tone. Especially between the blue. As for the snail, i give it a 8/10. Defintely your best. Again, just round the shading a bit more. Also, i'd recommend curving the left antennae beneath the eye, only because it looks a bit to rigid going strait up. I like the idea of the other eye wrapping around it though, and recommend you keep that anatomy factor.
I'll leave you with that, since it's a mouthful to write, and an earful to read... (that sound's funny actually, but is technically true on the internet...)
You have some good work here, and good ideas. You just need to keep touching them up! Keep trying though... and of course...
Keep Spriting!