Here are the steps on the Sproggiwood promo art, as you can see it was quite a complicated picture to work with. I started by doing a simple 3 value composition based on a pencil thumbnail, then added simple color and lines on top of that. I think the first steps actually have quite an interesting ink drawing look, it's feels bad to loose that to go to the painting.
The slimes ended up being extremely tricky to paint too, for the simple reason that it was incredibly hard to find any reference that would apply. I can hardly buy jelly at the store here, and all the jelly photographers seem to think white background and photographic lightning are the bees knees. I think taking that into account the finished result actually looks surprisingly good.
Another time consuming bit was the pile of leaves, you wouldn't think that it would be hard to find good reference pictures of them, but for some reason people don't seem to think that seeing the details on leaves is important. As it was a focal point I really wanted it to look right and interesting, though I suspect I might have overdone that a bit.
For more info on what I'm up to see my blog.