I'd suggest trying something a bit smaller.. work on the sky a bit more, only dither to add texture or if it's adding to make it smoother. Half this size would be good working size imo and try not to use soo many colours.. I understand that it's armageddon so im not going to suggest you add a pretty tree or any foliage but you would still expect changes in the land, hills, mountains, rocks? Atm it just looks like flat land off into the horizon. The crate really looks odd there because it's not following what perspective you'd expect. Your character looks very stiff also, look at your own arm, look at references to get the postion right, even ask someone to stand like that and sketch out what you see.
I made an edit but it ended up looking completely different, didn't tackle any colours, just suggesting how I think you should lay it out, maybe add a city on the horizon? Mostly my advice would be to keep your work clean, don't dither as if you're manually spray-canning, keep your outlines smooth and don't let your pixels stray (there are noticable mistakes that make this look rough and bitty). Working with silhouettes shouldn't be so hard, you can't get many noticable details in so stick to adding in highlights and hinting shapes, the reason why im suggesting this angle is because you can add some highlights on your character without it looking pillowshaded, plus a character in the middle of the screen seems so generic.
welll goodluck with this, I hope you take any of my suggestions into consideration.
