nice work, prefer the b\w version. 3rd one needs some more contrast and lighting to match the orange of his helmet.
Thanks For the colors I mainly use Color Balance, Channel Mixer, and curves. I never really liked gradient maps for some reason.
I like bother versions of space but im feeling the color more than b/w as for halo tag, its really washed out and as said should add some contrast and brightness to match the helmet. mabey render some lighting effects to.