I paint at around 6000x4500 mainly, you got much to learn young padawan
But those definitely are some huge pictures, you could always halve the size of the jpeg's for us, those barely even fit on my screen
Some nice stuff though, I always like it when artists paint a bit of environmental stuff. If you want some tips;
You definitely need to work on your anatomy on, at least from what I can see on that soldier. there is some weird stuff going on there. Try and bend your own leg in that angle, you'll realize it it not really possible unless you have seriously broken something
Another thing you should think about is the overall shading. You got some pretty good shading most of the time. But it's mainly in folds and edges, you need to shade stuff like all around as well. Like the snake monster. You have shading where it is most needed, but due to lack of overall shading it tends to look very flat anyway.
Also, on the sword, try and just do a black-transparent gradient over the whole sword, from bottom to top/where the lighting hits. And you'll notice it will look much more believable and real. Don't forget that light falls off. The overall object is much brighter where the light hits compared to further away from it. But you've used the same values all over the whole sword, and that usually ends up very artificial or flat.
It's been a while since you updated this with any new art. You should post us moar stuff homie! I'd love to see more scenes of yours, the space ship on the coast is really nice.