The second one is probably my favourite so far, although it only took something like 20 minutes.
I've literally done dozens of these in the past days, most of them aren't really worth showing though. I still feel like I'm barely scratching the surface of the whole approach.
Take a look at the "finished section" of ConceptArt Forums, there have been some fantastic threads lately. Off the top of my head, I strongly recommend checking out the threads by James Kei, Marko Djurdjevic, JasonChan, Carl Dobsky, Gezstar, RasselTassel, steak-tron and Aleksi.. I'm sure there's more to look at. They are all on the first page as I'm typing this, so go get'em while they're hot.