Mercury's concept illustration

[Mercury]

Here are some concept drawings I've been doing for a web comic I want to do.I want it to look good, but I'm also utilizing it as an opportunity to learn how to paint better. All are done in Photoshop, except for the last one which is Corel. You can see more of my work here: http://mercury24.deviantart.com/
Comments are appreciated.

[FrankEdemia]

These are pretty cool! I especially like the portrait drawing.

For the underground cathedral-type drawing, one piece of advice I can think of would be to make the floor a little less "busy" on the details. It tends to draw too much attention to itself, which draws the eye away from the columns and characters. There's a good atmosphere in this piece.