Thanks for posting!! This room is great and has a lot of potential!
Right now, since the room is empty, the blue carpet seems overpowering/ dominant, but once you start filling your space up with furniture, it will become more of a team player. I would definitely not bring too much more blue into the space, perhaps smaller accent items (versus a larger showcase like bedding.) I would also recommend bringing in different shades of blue. Since the carpet is lighter, some navy or ultra pastel blue will be nice complements without being overpowering.
Gray is a great neutral, so if you can some furniture that has gray finish (or even a little silver?), that could be a great way to bring that into the mix. Once you have the gray and blue established, you’ll see where and how much to bring the yellow in.
I’m super excited for you to decorate this space, I think it will be super cool!
Mr. Kate & Team