So I didn't save as many steps along the way this time as I sometimes do, so it's a bit less comprehensive, but I just wanted to give you a look at the way it started off as a line drawing and turned out the way it did.
I got pretty much all my composition down in the first rough pass, which was actually surprisingly painless for this piece (sometimes it can take a long time to be happy here, but it's important for later).
Considering I wanted it to be a pretty detailed piece overall I felt it would be less daunting to tackle if I planned it out with some tighter linework to begin with, which is where I worked out most of the intricacies of the logs and roots, and worked out the 'realistic' design of the different pokemon, so that I could just focus on the rendering when I got to the painting stage.
The 4-quarters sort of reveal I have in here is pretty much the order I did it in, but I didn't 100% focus on each area as I went, there is always a lot of jumping back and forth around the canvas as I go - I just thought that it'd be a bit easier to show it pop up more gradually looking at this, since that's all actually on one layer. So, the rendering is all pretty much split onto 4 layers - the very first gradients that I did the lines over, the first rough shadow pass (under the lines), the main bulk of the rendering, and finally most of the foreground fish, who're on another layer to make painting against the background easier.
*edited in - I think one of the things I did differently this time especially was hide the line layer, normally I keep it because I like the shadows it keeps, and some finer details that I don't have to repaint, but since I wanted it to be fading into the murky water I liked it better without it.
I wasn't working too big, the file's about 3800px wide (which is sort of smaller than I usually work, actually, but I only really thought about that about halfway through >.<)
Edit; since people were asking, I think this piece probably took about 25-30 hours (I got most of the linework done one night last week and then the painting was most of this last weekend).
Hope this is interesting,
final version is here -