One thing about 3D artwork is that the colors can sometimes look too perfect. You can reduce this by adding some a film color effect. My favorite way of doing this is with the Curves tool. Add a new Curves adjustment layer (Layer > New Adjustment Layer > Curves). Switch the channel to blue and drag the points towards the vertical center – this will add some blues to the shadows and gold to the highlights. Switch to the red channel and create a very slight S curve. Switch back to the RGB channel and create an S shape to increase the contrast. You can adjust the opacity of this curves layer to reduce the effect.
Here’s what the image looks like with and without the film effect.