I think a little more background would be useful here, Fafnir. Is this army a town based army, that may have cobbled streets and bases, or is this army very wild, with plenty of foliage and grit? What season is it? Do you want water/marsh bases? Just some more general info would be good, so we can give you better advice.
From what I've gathered though, if it's from Ostermark then some bases with a mixture of both normal and long static grass, perhaps with some rocks sticking through the long grass would look good for that wilder sort of style.
Very nice model though. I think you chose the right colours for you army, they look very nice with the browns. The quality of painting is excellent as well! Top marks for skill, especially since this is only a 5 point free company man.
Duellist