I like the second and first. Very cool work!. It seems you like the pallets of greens/cyan and then classic b/w. Ever make stuff in other schemes? Well done overall mate. EL
I really like the third one! Especially because I'm reallly into space and stuff. The first one is nice too. The second one just needs some more work with darkening on the left imo. The fourth one is alright. The last one... It's got my two favorite colors, so it looks nice to me.