Next up, I believe I have the scale that I want decided. Not a big region by any means, but big enough. At the scale given in the map, sea trees are one kilometer in diameter, which might be a bit too wide. The coral pillars in the map are also 1 km wide, and this is something I need to make new brushes for, if every one of them is that big, they'll be too uniform. The giant mangrove forest is broken up enough that I think it looks fine without messing with that. I still haven't placed any of the new Marishrooms, but mostly because I don't want every map feature to be in every place all at once.
I also added in my current version of the sea-swamp kelp beds, using the small galaxy brush from GIMP. I actually kinda like it, but I might run an emboss/bump filter on it to see if it makes it look any better.
If anything, I think I need to get more than just the five variations of each brush. I need something more like 20 variants per brush, and sometimes including smaller features.