You've already seen most of these figures, if not all of them, prior to their basing. I always feel that figures aren't complete until they have proper terrain to stand upon. There is something about green that complements the figure. I always say that it's a decorator's trick or a butcher's trick. Decorator's trick: in order to join rooms of different colors you use plants in each of the rooms. Butcher's trick: in order to make your meat appear redder and more appealing, add green paper backing or that weird green foliage to the butcher's case. In addition, the base of the figure changes the mood of the figure. For instance, below in the first picture, the female necromancer; imagine her on a sparse base with no foliage, just charred rocky debris. It would seem desolate and foreboding; which would work equally as well as the sparse grass. The sparse grass just doesn't seem as gloomy and I happen to enjoy how it makes the green in her staff and the green of the skeletons pop.
So one word of advice, "If you are ever a titch dissatisfied with a paint job; wait until you base it and see how you feel." The black of the stick or base you've been painting on is actually sucking the color out of the figure. It's an optical illusion, like when they suggest wearing black to make you look thinner. Dark colors make things look smaller but they also wash the color out of what they come in contact with.
I hate having to paint figures that I like. They are like children; I give them a little bit of life and I don't want to let them go when the time comes. I looked at Bob the other day and said with a pouty face, "Do I really have to send them?" He of course said, "Yes" and laughed at me. But, now you also know that I put a lot of love into what I do.