I reeally like your 2nd, 3rd and 4th painting. Specially the design of the two beasts.
The one with the guy on the bike and the robot could be cool with a better lighting. The robot would need to be darker to create depth and emphasize the biker.
Well,since these pieces are featured in finished artwork thread I thought that I should not post them here,but since lots of people post finished pieces as well in the sketchbook I might as well do the same.