Wow, you certainly begin a lot of projects, I hope you will be able to finish them all!
I see that you have now finished your contest entry and it looks quite good
I would have altered the tail a bit more however, the bend in the beginning still seemed a bit too sharp. I did this weird section thing (file name critique 1) to show you how I would have drawn it. You were VERY close, but it still didn't come off as graceful as it could be to me.
I hope you don't mind
For your flying dragon picture, I would go with the top one. The bottom one is very confusing with all those limbs and fingers being visible, plus it is much easier to work with the wings being as they are in the top picture rather than the bottom.
Vampira looks like she's really coming together, but I shall help you with your boulder/rock situation and maybe a few tweaks with her hind legs.
For the boulder, I suggest just finding some awesome pictures of them and sketching them first before doing a final version. I found this boulder http://www.brandywinequarry.com/images/boulder2-lg.jpg
and it looks very similar to the rock you chose. I simply applied this boulder to the rock Vampira is sitting on and I came out with the file labeled critique 2 Messy I know, but I tried to get the biggest feature in the rock to show. It may be annoying to add all that detail in, but, it will make the rock look believable.
Vampira's hind legs look fine, but the feet stick out too much. In regular animals, and in the cheetah pictures I showed you earlier, the back legs are behind the front legs rather than in front, or in line with. I did a red-line to show you what I mean (critique 3). Also, the calves are slightly broader near the knee and slope in near the ankles.
Also, the elbows of an animal, usually line up with the knee when sitting down and standing up http://visual.merriam-webster.com/image ... eeds_2.jpg
Hope I could help