I would suggest one focal point wall painted John Deere green with huge logo painted on the wall other walls neutral. Maybe sleek black furniture , black rolling toolboxes for night stands, etc. when he gets tired of John Deere then just paint over the accent wall and you're ready for the next theme.

I like your plan but I don't think a pattern on the bed wall is a good idea. The carpet already has a lot of pattern so I'd keep that wall a solid, dark color, from the rug. Add some sparkle like mercury lamps for the bedside tables for interest.

Buy the bedding you love and then go from there to doing the rest of the space, paint is cheap so leave it till the end of the process and match to something in the bedding would be my suggestion.

Hi there, this is very touch. But you have discovered the base principle already, soft materials or materials with a lot of surface area absorb the sound. Just shooting out some quick ideas here for you: A soft and thick rag or bath Matt on the floor. Curtains are a good sound absorber, but not to much in a moist bathroom. Potential mold issue ;-) Another idea could be to hang bathrobes on hooks or a fabric laundry hamper onto the back of your door. If you find its still not enough.... since your walls are already tiled. you could do something on your ceiling... like a timber slat ceiling or a painted plywood paneling with holes in it. Make sure you use polycaprithane paint for moisture protection on the timber.... hope this helps. If there are questions or you need more help, feel free to send me a message. Cheers Gunnar