Thanks for the responses, guys.
I made this with Perfect World DF, so relative elevation, wind direction (which determines rainfall), and drainage are about all I have control over, biome-wise. There is a Brush tool that can be used to spot-edit the map, but it's pretty finicky. I'll see what I can do, though.
Probably a rounding issue, but having a land bridge between Spain and Africa feels off; so does the one between Denmark and Sweden, though historically it was used to cross when frozen over during winter.
I thought about breaking those up, but I kind of like having a separate name for the different bodies of water; instead of just one "The Big Blue Water" all across the map, the Atlantic gets one name, the Mediterranean another, and the Baltic and Black seas likewise. It could also facilitate Adventure Mode travel, what with the lack of boats and all. But I'm not averse to splitting them apart.
As for mountains in Scotland/UK, those mountains are small enough compared to, say, the Alps, that they just kind of disappear. If I raise the cutoff generally, then unsightly things happen, like all of Spain being one huge mountain. But I could probably spot-edit some peaks in there. I don't know about plains, though.
Well if you want my opinion, I think Iceland is located a bit close to the UK.
It is. The heightmap has it so, since it's a "Europe" map; and otherwise, it'd be so far away that I'd have to extend the map dimensions accordingly, thereby reducing detail.
I don't know how much control over volcanoes I have, but I'll try putting a hotspot under Iceland.