2D Game Artists- Resources, Tutorials? Thread

So I'm working on a game with.. well, lot's of metal. I've tried making brass, copper, steel, all-in-all it comes out decent-looking, but nothing ever looks quite right to me.
So, are there ANY good tutorials on 2D game art (not pixel art)? I want to know how to make graphics for 2D games that are a bit higher resolution. I get by, being completely independent and mostly a programmer, but nothing I make looks quite as good as it does in my head. Any suggestions, resources, anything would be greatly appreciated. Thank you in advance!