Maybe book shelves n storage bin drawers !?
Decide what you are using the room for, play room, home office, guest room ? Have only those items in the room, redistribute the remaining & give stuff away. Best of luck !
Get all the clutter and stuff out . Repaint. Look at it empty . Reimagine storage do you want open shelves ? Do you want things behind doors? If you have access to an ikea go look and buy. Have themhelp you but all stores have basic shelving or bookcases that can be reconfigured and dressed up or down .
If you can build do so . If there are kids ,have kids cubbies below shelving where they can access and clean up . Attach shelving to those cubby units secure all to your walls .
Buy some cheap frames for kids art white or black whatever you like ! Love kids art .
You cant see the possibilities for the stuff .
Good luck , enjoy and make the most of what you have ! Sell the stuff that no longer serves you to buy New !