Nice work there, top 2 are a little dark think you need to play with curves that shall brighten it up a little in the dark areas, all in all nice feel to the sigs,
Kudos for using METROID .
I personally am a monotone type...(;_; Im boring)
But I really like the colors you used for the three in the middle. I would sugget perhaps a change in font? And great use of pattern ^__^