Making my room more cozy

Here's the deal:
My room has blue walls, some holes and white marks on them. Previous lessees have tried to hang paintings in the walls (which are concrete), so here we have quite ugly looking walls (I'll post pictures later on).

So what to do with them? I have pondered that about an year and now I come up with an idea! I'd like change my room to forest! Lots of plants, forest posters and moss-like-carpet!

That forest poster should be something like 2x4 meters or something like that. I know couple friends who could make posters if I pay them. In their school they have poster-making machines (don't know the proper name). And I have few plants already here. It's interesting to see how my room will look like. But now I'll just cut some forest pages from magazines to starters, so I wouldn't forget this.

~ MyLillian