There's not much difference in brightness between foreground and background, making it seem flat as if everything is the same distance from the viewer. It's much too bright for a night scene, and it's difficult to tell where the light source is. Some cast shadows would show where the light is coming from. You could simply show the moon in the picture to make it more obvious that it's night. The pose of the kid looks a bit 1-dimensional as well.
It's not clear to me what the relation between the kid and the lizard is. Is the kid its friend or its prey? The lizard would seem more like it's hunting if you gave it a pose to look like it's sneaking up on the kid. And it could use the tail to either grab the kid or distract him before the lizard makes its move, which seems fitting since it's already there and the kid is looking in the opposite direction.
Your color ramps seem to have very random leaps in hue and brightness. The result is a bit jarring. Maybe you could try to start out with straight ramps with more regular steps in brightness, and then compare the ramps and look for similarities. For instance, if you find two colors that are fairly similar, you can replace them with either one of them or a mix of the two. This way, the mixing of the ramps would serve a purpose, and it would also be more subtle.
If you start out with a grayscale or more or less monochromatic palette, you can add more interest to it by looking at where the colors are used. If you have large areas of a certain shade on elements that are supposed to be the same color and not much of it elsewhere, you can add color to that shade to fit those elements (shades on leaves or flowers, for instance, could have a green or purple tint, respectively). The color would mostly be on those elements, but it would also be a little bit of it in the rest of the image, so you'd unify the image without blending everything together.
Desaturate the darkest shades. Keep in mind that the more light there is the more color will be reflected and vice versa. There's not a lot of light at night, and that would make the scene look more monochromatic.
The darkest green seems really out of place in the background since it's very saturated, and too different from the blue colors in the rest of the ramp. For a night scene, it would fit better to move the darkest shades towards blue. Blue colors also seem colder. The warm colors of the kid's skin, shirt and the lizard's tongue would stand out more this way, since red and yellow seem warm. You have too much red in the rocks now, and that makes it blend together with the kid, making him more difficult to spot. You want to draw attention to him with either contrast in brightness or colors, and right now, there is neither.
Composition is also important when it comes to making things stand out and making a scene comfortable to look at. You can use lines to guide the viewer through the image, and add interest by using bright and dark areas and balancing them against each other. There's a lot to keep in mind, and I'm sure there are a few things in my edit that could use improvement. I think someone posted a link to
this blog here. It has a lot of tips regarding composition, and I've found it really useful, so take a look and see if that makes it any clearer.
