This is already my second post today, and it's close to midnight here, so I'll keep it short.
Paul Usul Fluegel who's creating DwarvenKingdoms gave me a hint on how to make the trees in PocketCrusades a bit more beautiful, and he was totally right, have a look:
|Before - Without AO on the trees|
|After - With AO on the trees|
I had Ambient Occlusion turned on in my light mapping at all times, however, I did not notice that the Unity Importer had "Generate Lightmap UV's" turned off for the tree models.
Well, now it's done, so thanks Paul.
Good night everyone!