Get it flocked.
Are we talking about the cam cover or the plastic cover that you get on most modern cars?
Metal cam covers can be painted any way you want or you could get it powder coated for not a lot.
Plastic ones will need a thorough degreasing & primered with a dedicated plastic primer, then you can spray it up as you like. PG did a cool water drop effect with his Bora, which you should be able to find with a simple search.