Firstly, I think the effort put into this definitely shows; it's quite a dynamic and vibrant image - it has an epic and climactic feel to it.

The two things that catch my eye as a bit off in this are the difference in perspective between the characters and the background, and the lack of a sense of depth.

I'm not entirely familiar with the characters, so I hope you won't mind me referring to them as Red and Blue. With the perspective, Red seems to match up all right with the background, as he appears to be toppling off of this balcony they're both on; however, Blue seems to match this same angle as Red, relative to the floor of the background - i.e. she also appears to be leaning away from us quite dramatically. Because they both share this same angle, it's introducing a strangeness to the overall perspective of the image.

I think if you gave Blue a more top-down perspective it'd help deal with the strangeness. The ground itself seems as if we're looking down onto it at about a 45 degree angle, so giving a more top-down look to Blue would make her appear to be standing on the ground more straight-up. You could leave Red alone, as he'd still look like he's falling (which appears to be correct with all of the stone breaking behind him).

Next is the depth; this deals mostly with the background, itself. The immediate impression that I get is that there are bushes under this balcony; however, when I look at it more closely, I see that perhaps we are very high up over a forest with rivers, and that Red would have more than some scratches from twigs if he hell.

The far background doesn't seem so far at first glance because it is rather high-contrast and the colors are fairly saturated. You'll find that when you see distance things in real life, the atmosphere has a great effect on very distant objects and terrain.

Firstly, the atmosphere will begin to remove more and more contrast of details within silhouettes the farther away you go. Simultaneously, it will begin to add more and more blue tinge to distant objects; so we're losing internal details and adding bluish haze the further we get from the 'camera' (bear in mind, this changes depending on many factors, but for this sake we are talking about a scene during the daytime, with an Earth-like atmosphere).

At the moment, the highlights and shadows of the trees are roughly equivalent to the highlights and shadows of the characters, themselves. If you can lighten the shadows of the trees, and add a faint overlay of light blue to them, I think you'd really expand the range of depth in the image, and make the foreground much more the focus.

The bottom line is that this is a nice image, regardless if changes are made; perhaps these are just some things to think about for your next work. (: