I don't know if it's possible for you, but if you can, try lowering the aperture on shots like #1 next time. The background is too much in focus for me, doesn't really separate out the subject. #2 I just wish was a little brighter, that's my onl complaint. Try Sac's curves tutorial maybe, or try playing with Shadows/Highlights in PS. I like #3 a bunch though, it's all in nice sharp focus and the colors are good. Maybe try using curves to bring up the subject and darken the background (might need a layer mask if you can't just bring down the darks).
You need to pay attention to your backgrounds, in the first I don't understand the point of the chopped plant that's in focus. Is the snake gonna eat it? Hump it? What? Why has it been included with the subject? The green plants do not accentuate the subject's scaley texture as the rocks in the second. In the third, you've chopped the upper petals which contain the highlights. You shot midday, leaving you shadows in the lower portion of the flower, but nothing to balance the photo with highlights. Two other flowers are poking into the frame in focus, both are not central to the photo.