How to make it look like an 18 year olds room

How to make it look like an 18 year olds room

so while i've been gone my father decided to do something nice. he added another room to our basement for me & wants me to move in. now the room is bigger than my last one but theres one problem... it's painted yellow. like not in your face blinding yellow but the kind of yellow you would paint in a babys room. its hideous. now i want to move in, but i'm not sure how to make it look like an 18 year olds room. he refuses to paint it. now i already have black furniture, so i'm hoping that will help, but man, i'm at loss of what to do. any ideas? here is a quick picture...
this is a picture of my old room @boarding school...i miss it.
Fruits of our labor

Fruits of our labor

My room: or how to fancy up a rental :)

My room: or how to fancy up a rental :)

Hats on display

Hats on display

Pic post

Pic post

Whitefly pests

Whitefly pests

The garden – part of

The garden – part of