These are both nice, the top one's appearance reminds me of Slayers and the other makes me think of Escaflowne pretty cool. Although I prefer the look of the first one over the other it has a fair draftiness to it and the idea of it is focused.

Mostly on a whole, to help you improve the most I think you need to lean towards putting down some real Attitude into your work. You're coming a ways, but I think you are putting too much emphasis on the little partial bits of details too soon to make sure they fit scaled in your initial plan. Try to just focus more on the fullness of what you're trying to do as in the body curves and the imagery look that you were looking to achieve..

Hmm, now for Critiques at your request..

First
The first is pretty cool looking, the hair and eyes look nice and the staff looks interesting. I think you're tying yourself far to short in a knot what you are capable of doing. I would seriously love to see you add some true action and some real captivation to your drawings.

Now, I see you are trying to go for a calm/cool breezy feel in the drawing. I'd love to you see you target the perspective view in a more erratic way. Try bending the view in your mind in some way think of wind and how it blows capture something and go with it. This would allow you to show some real loose creativity in your images! I just want to see you give damn you, give way more into what you do! (jerk the lines more wild/smooth)

This is rather well, but it's really basic while I do like it I know it can be so much more. I'd love too see you give a more explosive outburst of energy and fun to this whole image. I'd love to see the body just more drawn out stretched from a viewpoint giving you some feel of gliding. Doing so would bring out desired features like the face in a more unique look so it's lush and captive..
(you draw a tad stagnant)

Also, I'd love too see you work on your curves and leanness that you put into your female figures. Like the limbs and such you jump way to hasty from point to point giving a simple curve. I think you need to try to capture some of those awesome curves that really define the body. Everything has lots of tiny difference in it try to glide more and think about capturing some of those awesome curves. The body can be cushiony or tightly defined depending on the pull of muscles. You don't have to add a ton unless you like that sort of thing but I'd like too see a bit of a sliver more or a pounce into your human anatomy.

Hell, Don't be ashamed to use a eraser if you can't get a line done right so quickly.. Specially if you don't use a reference expect to erase, change, and manipulate lines as you go till you are happy many times.. (draw light)

Second
This is pretty umm.. feisty attempt here? Heh, don't think that's quite bondage going on their.

The very soft looking long type fluffy feathers here made me think Escaflowne if you ever watched that anime. When I first looked at this I thought their was wind blowing on her but if you look it sort of looks like the wings are withering away instead. I'm not fully certain if that's what you were going for that was cool to go for it tho.

That's really hellish to do that well with just lines to make them stand out. I think to enhance the feathers you probably could've added a bit more twist and spiral giving them a uplifted type air cushion. I think it would've been cool if the wings were more cupped arched initially inward or outward or you could've had them extended fully. I think that would've helped you capture more of defined feel, it's a mixed signal with her current body stance.

Her face in this seems a bit too symmetrical in level when the face is turned like that with part of her face going back the eyes shouldn't be perfectly lined up like that. It makes her head look pancaked flat actually, the eyes should be a bit displaced slightly with a gentle roll curve below the eye on the eye that is coming towards us into perspective. Same thing should be done with the Eyebrows/Eyelids just something you pick up on later how things change to perspective. (can be a few ways)

Hmm, as far as the details go you need to really focus and do them with careful consideration if you want to really enrich something using them as a further extension. I'll say you don't have to go ballistic with fine tuning details to make something cool or outstanding it's really a style preference.

That is quite a taunting outfit you went with, depends what you were looking to hit with. I think the corset you have would be alot better if you had it more inclined to her hips wrapping up to her breasts. You would normally see a really tight squeezed look if you ever seen someone daring enough to actually put that on lol..

Alot of cloth details you could get really intricate with if you wanted. Like with the strings cutting back with different tensions and such all varies to the feel you are trying to carry out. (just something to think about)

Maybe you just overlooked this or got a bit to carried away. Those straps that run up her thighs should probably be on the outside and another on the inside. Looks like you placed them on a bit too symmetrical and it doesn't particularly look good downside and it throws off the picture. Just a little example if their is only two leg lace straps do this same with the buckles. The left lace strap on the her leg should probably be on the very edge slightly lapped over out of view. The one on the right should probably curve beside her butt cheek and run towards the front with a inward curve.

Nitpick her chest looks a bit odd I believe your missing a little indication of her breast line their or some type of slack line is needed inbetween if that is cloth.

I finally came around to commenting on these, I hope some of this actually helps you or someone.. That was pretty tasking to type this, I'll try not to write a novel in here..

As for the second, I think her chest isn't shaped quite right and her hips could be a little wider.