They have a wall in the living room designated to notes and pictures that they have collected over the years. (It's started by Petunia making a list of rules and sticking it in the middle of the wall. One of the rules is no putting things on that wall. D.C hates rules)
In 4th year they began going to the Shrieking Shack since they now know it isn't actually haunted. They decide that it is their new hangout whenever they don't want others around and start to spruce it up.
The trio asks for help from the house elves who gladly comply, as long as they use the trio's money as they don't have permission to use Hogwarts money.
The kitchen has orange tiger lily walls, D.C's favourite colour.
The bathroom is jungle vine green, Brandy's favourite colour.
The dining room is navy blue, Pete's favourite colour.
Living room is striped festival yellow, calypso coral, and ponsettia red. They all have a hand in choosing these colours and all buy furniture that match the rooms.
They allow Fred and George to use the upstairs as a testing area for their stuff with two conditions. One, no destroying the walls or anything downstairs and 5 galleons a month. Two, no coming up during the full moon and don't question the crazy restraints on the door.
Sometimes the trio help them out with the design and ideas.
Petunia uses engorgio charms on the Shack to make the rooms larger once people start piling into the room of requirement. She makes bedrooms for the D.A leaders and tells them the only loud noise they can make is shrieks and screams.
7th year the Shrieking Shack becomes the decision room for Dumbledore's Army. It is connected to the Room of Requirement through the same tunnel as the Hogs Head.
