at first a quite nice composition and the first dio withthis "sneaking in the jungle" them i really like.
but there are some points ,id like to mention even though i hvent done here anything else then critising people so take it als constructional critic.
1.the water seems to me to blue a green colour would ,in my mind, more fit
2.the marines could get more dirty (and mybe wet, i mean if you walk through a river you probably wont be able to keep totally dry)
3. the grass on the ground looks strange, i would make it even really long or just put it away.
4.ok this is quite small: the guy in front seems to be crouching, so i would build something to give him a reason to crouch (like some leafes)(and group the others behind him
but thats just what I think and i would have it build with some other things (make it moore like the cover of the kit with something like a floodet jungle) but thats what i think and that shouldnt smaller youre work