This one was nice to do, although I'm not a huge fan of orange, because it made me think of autumn. Since autumn has just begun here, it seemed fitting. When choosing the wings, monarchs seemed a little too obvious, so I went with some random type of orange butterfly that Google gave me, which I don't know the name of.
There's something a bit off about this one that I think has to do with lighting, but for the life of me I wasn't able to fix it. See if you can spot it for me and let me know.
I really do quite like this picture, though as you say there is something a little off about it.
As far as i can tell, it simply comes down to defining the shadows, and separating the fore and backgrounds.
One of the most distracting things in this image is the barely noticeable difference between the leaves and the dress. I would suggest introducing a few darker reds and browns amongst the leaves, and possibly a few dark yellows. That should make the foreground pop a bit more.
As for the foreground, I think just adding a bit more depth of colour to the shadows would do the trick. Orange is one of the hardest colours to do shading for, as we automatically tend to try and shade with reds. I would try shading with some brown and then add a bit of colour to that.
I hope that helps you. But as I said, It is still a lovely artwork ^_^
Okay, since I'z is lackin' in the Premium Membership thingy....
Since the light seems almost entirely above her head, then I think the main issue is simply that the shadows aren't quite dark enough to really bring that out, especially in the lowermost folds of the skirt. Additional shading beneath the bust would help as well, and impart more definition to the shape of her body. The additional shadows don't need to be very dark, just a little bit more in the way of shadows to define shape and contour, which is getting a little lost in the vivid background shades. Aside from that, I can't really see what else might be done or required.
All in all, though, I think the execution is very well done, and certainly an eye catcher. The devil is in the details.