I like the color variety in the shadow splotches for the background of each shown character, it gives the picture a bit more depth and variety, and each chosen color makes them pop out even more, so that's some pretty good stuff there.
They look nice -- but the arm on the right on the lower right one seems a bit off. Like it should be moved up a bit more in my opinion, as it doesn't look level with the other arm.
Though... the lines of the lower left seem a bit, unnoticable compared to the other five.
Otherwise these are pretty great.