For some reason this reminds me of a flag, perhaps the Jamaican flag? Maybe its the colors or the rectangular design. Also the place the two squares meed seems off for some reason, maybe it's not aligned? Well I don't know exactly what is wrong, but something must be, because the circles are not equal distance to the right square. Nice color scheme though.

Did you change the aspect ratio of the photograph? If so that would explain why the bird looks somewhat longer in the mesh. It seems like the line between the beaks should be a little more emphasized, because right now it seems like its almost one beak. Other than that it looks pretty good.

I think some of the colors might be a little off. It seems like the sky should be more of the color of the ocean you have and the ocean should be darker. What you could so with the water under the whale is play with the level of transparency so that the water looks more realistic. Also the whale looks pretty well done.

I think the main problem here is that you might have too many mesh lines, which as a result makes the transition from the bottom of the mushroom to the top have lines. The top left looks good. Maybe pick colors that would blend better for the places that have lines of different colors, like colors that are closer together give a better blend.

For some reason the magma just feels out of place. Maybe it's because it's so bright, it ends up taking all of the attention of the viewer. Overall the objects look very natural, and the picture looks very organized.

The bridge was taken out nicely, and the alien and predator were placed nicely, execpt the predator's head is pixelated for whatever reason. Maybe put some sort of shadow under the boat if it is supposed to be floating, and blur the line between the city and sky a little because the line seems a little too hard.

The right side seems a little blotchy, and the shoreline is visibly "shopped" as the ocean is visible between the sand. It looks like the bridge was taken out nicely. But I think we were supposed to insert an object into the picture...