Here is an attempt at a black-leaning treefolk - a sinister deciduous bastard that awoke in the "Shadowmoor" set. It's just fun to draw gnarly branches!
And secondly, a couple very very early versions of what would become the much more human-looking Kithkin. I think the vaguest early description was that Kithkin (or whatever we were calling them at the time) were simply the replacements for humans in Lorwyn. And we went from there.
These early Kithkin concepts were probably done in the first day or two of concepting. In that stage, at least for me, I'm just throwing down anything that seems like it might capture the flavor of the setting to see what the art director is looking for. It's the buckshot approach - fire off a large spray of smaller drawings to see what hits the mark and go from there.