You don't want to just put c4ds in empty spaces, but rather have them compliment your focal. If it's put in places that the focal is not around, it'll draw attention away from it. (focal being spiderman)
Tag size. You see that your tag is very long, but there's a ton of empty space, (which you filled with c4d) You should shorten your tag length, not so much that it becomes cramped, but not too long so that it doesnt draw attention away.
Colors, gradient maps are okay if you're starting out, but try to work on using natural colors from the stock, with color changes from like lighting and such.
lighting/depth. 2 things this tag lacks. Lighting and depth go hand in hand, (usually) it creates more realistic look, and not so flat. Like Spiderman blends in with the background, and theres not too much of a distinction between them (looks kind of flat)
Just try adding a stock for a background and blurring it, adding a light source, and burning places where the light should not be hitting.
Overall, just work on the basics, and you'll get the hang of it.