Decorating a bedroom for two children requires negotiating with both of them for a space they feel comfortable in without intruding on the other child. This can get a bit tricky when a girl and boy share the bedroom, as they most likely won't share too many of the same decorating ideas. Talk to both children about their ideas and expectations, and try to find common ground.
Decorate the room with a colour scheme both children can agree on. If they don't agree, choose a neutral colour for the primary colour in the room. Then let each of the children add an accent colour. For example, use chocolate brown and cream as the base colours in the room. Use navy, aqua, light blue or lime green for his side of the room and light pink, hot pink, red, aqua, purple or lime green for her side. Incorporate a pattern that works for both sides, such as stripes. Or, use the same colours throughout the entire room but keep his side in stripes and hers in polka dots, or his in squares and hers in circles.
All four walls can be painted a different colour if they agree on a basic colour scheme involving four different primary colours, such as red, green, blue and yellow. Or, paint two walls in a neutral colour, his wall in his favourite colour and her wall in her favourite colour.
Many themes work for a boy and girl, or can be tweaked into something special for each of them. For example, use a western theme for a cowboy and cowgirl. Under-the-sea themes work if they both like fish, whales, dolphins and other sea creatures. Tweak it a bit by adding mermaids to her side of the room and pirates or sea monsters on his side.
Use a knight theme on his side and a princess theme on her side, while tying it all together with a castle, horses or other royal details. Many different animal themes work for boys and girls, including farm animals, zoo animals, jungle animals, Noah's Ark or a circus theme.
The furniture for both children should complement the rest of the room and meet the needs of each of them. Bunk beds can save floor space, giving them a larger area to play. This may not work if they don't get along very well. Loft bunk beds will give each of them their own bed and their own retreat underneath their beds. Two separate twin-sized beds could grace opposite walls, allowing for more creative decorating if they don't agree.
Provide ample storage for each of the kids without disrupting the flow of the decor. Use a large bookshelf and assign each of the kids their own shelves. Get baskets or storage containers in different colours so each child has his own space to store his items. Assign drawers to the kids, unless you have the space to give them each their own dresser or chest. Use themed drawer pulls to designate the drawers and tie it back into the room decor.
Privacy can be a huge factor when siblings share a room, particularly a boy and girl. Give them each their own retreat by adding a curtain or canopy around the beds that complement their favourite colours or specific themes. Stagger tall chests or bookshelves side by side with one facing his side and one facing her side if you'd rather partition the room. Just leave enough open space for them to play together at the opposite end of the room. Another option is to hang a curtain in the middle of the room that can easily be retracted when the kids want to play together.