I understand you a lot, eheh, because, I repeat, I'm the last one who can draw a background decently ^^ The important thing is never give up! If it's the first time you've done a scene, well, you have the right temper, because nothing is worse than someone who is afraid to try something new. And so... good work for the future!  

I decided to critique this picture because it's the last one and really caught my eyes! <img src="e.deviantart.net/emoticons/b/b…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="366" title=" (Big Grin)"/>

First of all, I like the composition: the proportions between the two sides of the rectangle is good and the figure and the background fit very well the space you gave them, so that there is an half which belances the other half.
Secondly, the details. You're gallery is full of art nouveau-like pictures but I see that, unless you're going to plan a drawing which has to show one character, you don't put too much details, and this is sad because you have demonstrated a lot that you can do it and you have an eye for this complicated things! Bringing up as example the great artist Mucha with this picture, you can see how he emphasized his ability in decoration by drawing a creature of nature instead of adding a framework. And so I think you should have to. I don't know with what, maybe with a bush or something with the grass.
The figure, on the contrary, is very good. The pose is classical as it has to be, the cape is majestic, the shades are natural on the folds. The outline is thick too! Also, I like the colors you used. In the girl you managed to color with two blue which don't make her appear like the Virgin Mary, and I think that's pretty hard, because such a mistake would have been around the corner.
In the opposite the background is too faded. I know how hard it is to paint a background, because it happens to me too, but, since you're not doing an impressionistic-like picture I think you should have accentuate the texture of the trees with a thick line.
Finally, the golden framework. In iself is very pretty and curvy but it is the only thing which decorates the whole work... For this reason, it seems even a bit mismatched.

In conclusion the idea, the atmosphere and the girl are already put into the art nouveau genre and together look harmonized; you only should have freed your taste for adornement more. But don't worry, because you have what it takes to draw something eye-popping! <img src="e.deviantart.net/emoticons/l/l…" width="19" height="19" alt="" data-embed-type="emoticon" data-embed-id="577" title="La la la la"/>