DSS is 17, and we re-did his room last year, as part of an ongoing whole house renovation.
When I talked to him before hand he said he had no specific preferences, but said no when I suggested pink 
In the end we’ve gone for keeping it simple, with a modern industrial feel, but not too ott, as the house is a 1930’s cottage and I wanted it to fit with the whole house, but still feel like it’s his.
It’s mainly an off white colour (slight green tint in some light), with a small pallet wall, black metal bed frame (sort of old hospital style). The floor is sanded back oak, so neutral but warm, and he’s got bedding/rug/curtains that are in blue and grey tones, with a couple of pops of yellow.
DH built the curtain rail, a hanging rail (attached over an old Victorian pine chest) and a desk out of key clamp scaffolding and some scaffolding boards (sanded down and treated).
He’s got a couple of largish black and white prints, and a small plant that we’re all astonished he’s been able to keep alive for so long! 
Sorry, that was far longer than I thought it was going to be! 