So, I decided to make it slightly bigger. I see it now to be between 600 and 800 m² and can comfortably house around 50 people. I'm really bad with dimensions so if this is incorrect or impossible, please let me know.
I added the forest, dirt and undergrowth to the sketch. The first one is with the sketch for the river and ruin, the second in is just the clearing, to give some sort of an idea for what is going to be added later on. I'm still looking for some way to make the trees look bigger. Would making the Drop Shadow longer help? Comments are most welcome.