Very nice style. By "study", is it for achieving a particular style or are you trying to get better defining different types of surfaces? This looks more like a design sheet than a study. Maybe you want to make some studies from life/photos to get a better idea of how the light would act on different surfaces. If that was…
Nice design, I think what's missing is a reflective surface. I'm not sure about the blue fresnel light either, it doesn't really match the surroundings. I did a quick paintover:
Allan-p, the way you painted the chunky knight's armour surface looks cool, the shapes appear tangible. A lot of nice stuff in here, I think I'll join the sketch ride! A couple of quick environmental sketches I did today, playing with ambiance.
Never used a tablet before but I used to draw a lot, this is what I came up with after a week or two of doodling in PS btw it's a wacom bamboo tablet and I'm loving it so far.. but the pen nib is wearing down very fast, anyone has this problem too? I mean I was drawing for like 4 hours and I could already see it wear down…