This is actually a great start but liked Gaff said you need to bump up the contrast a bit.
I did a quick paint over, I'm not really good with environment so Ill share what i know xD
If you want to focus on the characters then doing what Demon said would be best. Try to use the environment to lead the viewers eyes to the 2 character. I kinda repainted a few rocks so its pointed at them.
Another thing you can do is to put the highest contrasting point near the characters. This will make them pop out more. The way you have the landscape is a bit hard for the guy on the right side. So just bump the contrast anyways.
Another thing I did was I kinda split the painting into foreground mid-ground and back ground by painting the edges of those cliff with some soft dusk? This help creates atmospheric perspective.
What you can do to bring this to a more finish painting is to try to use hard brush to clean and refine the edges. After that maybe you can try using some texture brushes or photo texture to give the rocks more detail.
Keep going man! Its a great start!