The first thing to plan for in home improvements is the practical stuff. The second thing you need to talk to family members about is the fun stuff.
Most people have colors they like and colors they don't like. They have things that interest them and things that don't. Get your family to talk to you about those things. Each person's bedroom, or bedroom area, should reflect his or her taste and interests.
A boy who likes green, football, and backpacking can easily have a sage green (it “reads” as more neutral than many shades of green if re-sale of your home is a concern) room with cream woodwork, cream interior shutters, and cream ceiling. Framed football posters and wilderness scenes might be pleasant. Bedding with a rustic motif (rows of stylized pine trees?) from L.L. Bean or Plow and Hearth would work right in. Add a touch or two of a bright color like red or yellow.
Does he need a desk in his room? A chest of drawers? A bookcase? Would he enjoy having a bulletin board? Even if they're small, most rooms need at least three lamps so that illumination is general and even. The shades are usually best in warm, neutral colors. (Light coming through green shades tends to make people look sick.) Lamp shades should be level and the seams should be toward the wall so they're not visible. When the bottom edge of most lamp shades in a room are the same height from the floor, the room tends to look serene and cohesive.
Hanging pictures usually look best if the bottom edges of the frames are the same height from the floor and level with each other, too. There are exceptions to this and every generalization of course. A grouping of pictures can have the bottom tier follow the “rule” while all of the other pictures are higher. A picture over a fireplace often looks good higher than the other pictures in the room.
Pictures usually look best when they have a relationship to furniture or an architectural feature. Pictures centered over a chest, bed, bookcase, or fireplace are good examples. Pictures don't tend to look good if they're scattered willy-nilly around a room, or if they're up near the ceiling (unless they're part of a grouping), or if the height at which they're hung varies wildly with no rhyme nor reason.
A girl who loves pink, the ballet, and swimming can have woodwork the same cream as her brother's while her walls are a soft pink (a pink with a hint of yellow in it tends to go well with cream), and her art work reflects her interests. If she loves to read, make sure she has a good reading lamp near her bed, or near a comfortable chair, or both.
A cream colored dust ruffle with widely spaced pink stripes and a quilted plaid coverlet in pink, green, yellow, and blue on a cream background might look nice. Add cream fabric window shades with large pink polka dots and I'll bet she'll smile.
The bigger point is to simply have fun with some of your home improvements. There is no need to look exclusively at practical matters.
