I've not put pen or pencil to paper for years. I keep meaning to. Even got some pads and pencils n'stuff but photography ends up being my medium of choice. I've seen a few things to inspire me recently so I think I'll have a go.
i think the top two are pretty good. the middle are kind of "blah" and the left one on the last row looks pretty cool. the right on the last row looks really good. so basically, the top left and the bottom right look pretty realistic. ^-^
Nice and loose, I like that. Great lighting and effective use of negative space. The statue and temple ruins are very good, there's a good sense of foreshadowing and oppression. You might want to try shifting your pallet colors a bit more to warmer or cooler (a bit too close to the middle spectrum) for a bigger sense of depth.
I hope that helps... and remember it's just my opinion. YMMV
*nod* understood. Utilizing a limited pallet gives you experience in controlling values, rather than relying on color to convey mood, depth or atmosphere. So learning one rule before learning a different set of rules.