Great stuff you have here, but I have a quick question for you.
Do you feel it's easier to add in details when the piece is larger compared to if you had a smaller piece?
See, what I do usually is just make the size of whatever it is I'm working on, and work from that. Usually I dont go too big either, but I've noticed how a lot of people go for the larger image and then resize it.
Oh, and while I'm at it, another question. I assume you use photoshop, but what kind of (personal favorite) brush(es) do you use and at what opacity?