Yeah, you could add more fog, or perhaps give the two figures a little more colour, or depth to them. The donkey, horse... looks sort of flat, I guess. You could get some reference and really improve the shape and believability of it. Your piece is also quite sci fi - so perhaps adding some details in the figures to link them to the background atmosphere? They seem like current day rice field farmers right now, which is juxtaposing against the other style you have in the bg, which you might be going for, I'm not sure.