I see I have some tips for you as well... (This is really gonna make me sound like the über painter... but... :bleh: )
All the models seem to be coated with very thick paint. This could be due to old paint, lack of shading or using too many layers.
The best way to avoid this is to use black ink. Get the details out.
You should also use water to remove the clumps that often occurs in Citadel paint. And highlight, highlight, highlight
Even though Space Marines are notorious for using one-coloured battle-suits, remember that the same colour will have different shades depending on the light.
Let me also offer you a tip regarding painting human flesh. The Citadel Flesh colours are crap, don't use them. Mix your own. I'll give you the mix-recipe when I get back home, but I remember that it included Human Flesh, Bubonic Brown, Rotting Flesh, Sunburst Yellow and some more.
Other than that you have a great eye for details. Just remember that even though YOU see the details, it is a shame if the others can't. This is where the Black Ink comes into the picture
Anyways... here is just a quick dabble in Paint with one of your models. This is the effect you would have gotten by using Black Ink. As you can see the details in the armor would be more visible.