Good tabletop quality !
To bring it to the next step here's what i'd do:
1) Be sure to thin your paints. Don't need anything super fancy at first, just water, though there are mediums and thinners and flow improvers out there as you get better.
2) dry brush and highlight - take the plasma coil. take that base color, mix a little white, and drybrush that area, the ridges will pick up the lighter color while the recesses stay darker, it'll create a good effect.
3) Wash - use washes to give the effect of depth and shadow, thin the wash and don't over do it. The bald marines head is a good example, a black wash on the face mask will bring out detail, and a flesh wash on the face will do the same. Also, i know painting eyes is a royal bitch, but flesh colored eyes detract from an otherwise clean and good paintjob.
4) To get rid of the shine, blast these guys with a matte sealer (i like testors personally) sprayed very thin and gingerly.