Well.... if it were snake skin or anything with scales, you could use an action (do a search on free Photoshop Actions)that create a metalic look on each individual scale.... or you could use a filter like Eye Candy Chrome to make the scales look metallic or go to the FARP website I believe there is a tutorial there on painting metal (there may even be one here LOL havent looked) With any of these methods though I really reccomend working on the scales individually, most filters will wipe out something like scales when applied, just keep your lighting all going the same direction and it should turn out nice looking. Hope that was helpful