Help me furnish/decorate my son's room!

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He's going to be 1.5-2 years old when he gets his room. His room is small with sloped roof which makes it so hard to decorate! The walls are blue and the floor is white, it's a pretty dark room because the window is small. Please give me some ideas! It's my first child so I'm not really sure about the "essentials" for a kid's room, besides a bed 😂