The image of embarrassed Neil is really funny, I like that one a lot! I'd say that one is my favorite of what you posted so far. He seems like a fun character and I hope to see more of him and your other stuff soon!
I'll move onto critique now. Hope this helps you out for when you draw next time. =D
What instantly comes to me when looking at your first image is the color of the pants. The purple is very bright and a little rough on the eyes; perhaps desaturate it a bit? As it is right now, it's somewhat an "unrealisticly bright" color for clothing, I think. Additionally, if you're able, try to make his legs a little longer and fix up the knee area - his right leg is bent strangely, as if it's broken/twisted.
Putting that aside, there's also the ears... they look like they're coming out from the top of his head so I'd suggest making the area where the ears connect to the head visible instead of being blocked off by his head. I'm hoping that didn't sound confusing.
One of your main weaknesses seem to be hands. They're definitely very hard and I usually can't get them to look 100% correct either, but the fingers on Neil's hand in the first picture are shaped and bent inaccurately. I'd recommend trying out
this tutorial to learn a little more about hands in general, it's very helpful. :D
Okay, moving onto the second one now!
I like the colors you chose here but the arms look very "rubbery" if you will. The curve of his left arm (our right) especially is strange and the hands/fingers could also use some tweaking (where are his thumbs?). The way the fingers are curled around the weapons is the main issue with his hands; it doesn't really look right. Try to move his nose down a bit, too - noses are a lot closer to mouths than you've shown here.
Those are really the only big issues I have with this piece, so onto the third!
This one is pretty good, though the shading confuses me. There's too much shading around the crotch area especially and the overall perfectly straight line shading is a little strange. I'm assuming you have your light source here (left side) but the way you executed it makes the character look a bit flat.
Finally up to my favorite, the fourth! :3
As I said, Neil is very cool, but I think the space between his legs is a tad too big. The tail should also probably be lowered a bit - its current position makes it seem like once it finally connects to the body, it attaches to his left side rather than the center.
Oh, and there's also the folds on the towel (assuming it's a towel)... there's quite a lot more folds on it than there should be.
These two folds tutorials could be useful, so try them out. :3 The hand with the towel looks too straight, too. I personally think
this is a nice reference for arms help that I am planning on using soon, so I'll leave it here. Definitely practice your hands when you can - it seems like you have a tough time with 'em in general (which is perfectly understandable, they're hard to draw).
All right, finally on the last picture! Whew. XD;;
Again, like the image before this one, the space between the legs is quite big. There's also the usual anatomy mistakes when it comes to hands... in this image specifically, the hands and fingers look much shorter in proportion to the head than they should.
That's pretty much all! Good luck with your next set of images, hoping you post them here for us to see, too. ^_^