I really like the work. But just some tips (not criticism because I like tips from people), use of shadow is important in making it look like its real mechanics underneath. You can use the burn tool in GIMP or a similar tool in another program like photoshop that adds a charred look outlining the skin of where you have the mechanics or shadowing the mechanics. Also another good tip would be to only place the open mechanics not over clothing like your open back and headless shots which I like unless you can play around to make it look like the clothes have been torn. Keep up the good work and play around with some things. Thats what I have been doing.