Updated

Oh man, I used to be really active in the Runescape pixel scene, it's kind of cool to see that it still exists.

Like nomadic cupcake said, I would work on the mountains in the background, and maybe re-do some of the shading so that it doesn't look too blocky.

The ground overall looks pretty plain. I would suggest maybe a remarkable landmark or something along those lines to add variety to the space. Maybe have a river cutting through the scene, or a building to add variety?

Another cool (but difficult) effect you might want to consider is to rework the lighting. I see the campfire there, and it might look good to make the lighting really dark, and have the campfire providing high contrast lighting to make the scene really sharp.

I would maybe work on the shape of the mage a bit more,  like it is now he kind of looks like a shapeless mass, I would define his figure a bit more. It might pay to make him larger, simply because the background is so wide that the mage (I assume that's the picture's focus) kind of loses emphasis.

Hope I could help.