When I was a kid my favorite book was Mashenka. I loved the story and the illustrations. I still remember how i felt when i noticed that all the furniture was the perfect size for her, and i always desire to have a bedroom like hers. Just like us adults do, kids need chairs, beds and tables suited for their size and age so they can use them as comfortably as we do.
Whenever you think of furnish a room for a kid think always in furniture that will fit the kids needs until certain age, because it is true that they grow really fast. Also, decide whether if you want a decor that will last long enough or just stand until certain stage of their lives, that will give you an idea of what type of color you want on the walls and the type of furniture you are buying for it.
Kids furniture allow you to experiment with all those styles that just never seem right for your age, let lose all your creativity with kids bedrooms, they will thank you for it, specially if you choose furniture that will allow them to create and play with the space and their imagination, here i have a beautiful example from smarin, a french design studio that creates one of the most amazing pieces i have ever seeing :
Last but not least, always allow your kids to choose their furniture, it was so frustrating for me not to have the last word about it.