If you fished the key from the bodem of the ocean, i think it could use a bit of rust and some more green tints(you know make it more dirty).
You can probably add some more cracks in his skull.
Also when it comes to lighting with spotlights make use of the linear decay funcytion (you should up the intensity to about 20-30, depending on the distance) and make the penumbra angle to about 5 and the coneangle to 35.
And give the light a dropoff(also depending on the distance)
And only make one light cast shadows (but this also depends on the scenery where the key is placed)
The model seems to be floating, you can also change the scenery ,to like a cave or something, to bring out the model some more.
And in the end an occlusion-pass to bring out the details
I know this was a bit long, but it's all with the best intentions