The wallpapers are undoubtedly beautiful. However you're gonna need some money to buy it and some time and skills or experience to apply it. If you are looking for something that would let you quickly and effectively decorate your child's room and is cheaper and/or easier in use you should chose wall stickers.
I think that one of their biggest advantage is that everyone can create their own composition from the same kit. Same product but plenty results. The designs? Countless. Everyone can find something suitable for his/her taste.