Try to reduce the Reflectivity of the bodywork so its not like a mirror.

Maybe add some dirt to the 4*4?

As its daylight, i`d remove the glow on the lights

Try adding some dirtmaps or a fractal to the specularity of the tyre.

Add an extra smooth level on the background mountain thing sticking out, i see some unsmoothed edges.

Thou adding a displacement you need to see what ammount of polygons you need to make it look good.

Maybe add some extra modelled rocks? Some twigs? Plants?

For your first model, you should be very proud, nice work!

Lets kick some ass to get it better eh