The fix is rather simple ... you just have sparse tiles that border the Clumpy tiles (separate the clumps from the empty space) ...
So you have a tile that "blends" the clump of forest into the barren space by having thinner forest, that slowly thins out from one side to the other.
Mind you, this approach sounds (and probably is) quite time consuming, and hurts the ability to make random maps.
Alternatively ... you make "tiles" bigger, with a small clumpy center of "active tile" surrounded by "border tiles", and you do this all in one space.
Highlight the part that you want to be the "active tile" and the rest becomes inactive (cosmetic) "border tiles"
Alternatively, you could somehow get Trees to Sporadically spawn on tiles that border forest/swamp tiles. Just use Asymmetry and alternating space (somehow).
Either way, making a Random Map generator with repeatable "awesome" is a lot harder than making a pretty screenshot.
I will agree that TucoBenedicto's screenshot is rather Favorable.
a couple notes about the screen-shot: I like the UI, with the exception of the mini-map. That mini-map looks nothing like the rest of the screenshot (or the scale is just way off). But I like how it shows how many settlements and heroes you have.
I guess the one thing that I don't like is how the "fallen" waters are LAVA (but it looks really cool, so I am honestly okay with it and I can look past its silliness)
The "evil water" being LAVA is rather artistic and makes for a cool screenshot ... but I'm not sure if it fits into the lore.