The simplistic style is very lovely to look at, and the colors look very befitting and clearly picked with consistency in mind. The lines aren't so much of a problem, as I feel they give an organic feel to this work. However, the shadows are a bit too simple. They're located directly under both miners, even though the light source is clearly coming from behind them from the torches, so their shadows should've stretched away from them in the opposite direction of the fires.
Either way, very lovely and simple piece which clearly had some heart put into it. Lovely job!