I believe a light grey would look nice behind the blue in the map - it needs to be a perfect shade of grey as grey is hard to achieve. Possibly experiment with various colours - I usually paint on board using sample pots first then hold them up in large sheets to see what suits the area... This gives you an indication of where throws of light will capture the actual colour and which shades suite the room without having to paint on the walls. The board base colour generally needs to be as close to your existing wall colour to achieve the closest match.

Its a really lovely room! what a great place for kids to share. I like kids sharing rooms. I think you need another colour to tie it together. I would suggest a blue tone.... teal, navy blue, duck egg blue. to tie it together. Its a little to pale and looks sparse, but actually isn't. I would leave everything exactly as is, BUT, paint the back wall behind the bed teal and find a simple navy blue wall decal that is fun and kid- like maybe one with a sillouette of a boy and girl playing. I would paint the wall behind the sofa duck egg blue. Then I think it would suit both kids more and look more kid friendly. the blues will balance the pink and cream, but because you have a pale carpet i don't think it will look too dark. don't worry about making it totally kid like, its a room they will grow with, not a kindergarten, and it also needs to peaceful and restful for sleeping. besides with their art on the walls and bright toys everywhere it soon looks bright and kid like. Good luck!

No experience with babies actually - but seems there are endless combinations - this was just the first / type in and select "Stories" for good articles like this with at least 2 ideas. Many "Photos" on houzz. "Shop" too. [https://www.houzz.com/magazine/guest-picks-desert-beauty-for-the-babys-room-stsetivw-vs~29205805[(https://www.houzz.com/magazine/guest-picks-desert-beauty-for-the-babys-room-stsetivw-vs~29205805)

There is so much you can do with the rug. You can go with a modern feel by bringing in metals, glass and creams with pops of orange or greens. You can go mid century modern by emphasizing the orange or even traditional with woods and beiges with hints of colors. If this was my starting point for a room that just needs to be cozy and comfortable, I would do a statement bed with darker wood. I would keep the curtains very light, and also the bedding. As there is creams in the carpet, I would steer clear of white, but use off white / beige for the bedding and curtains. Then I would use the orange and greens as accents in the room. Good luck and enjoy the process.