Kids bedrooms can be tricky places to decorate, because as kids grow up, their personal styles and interests change. A girly-girl color scheme with bright pinks and purples may outright disgust a tomboy daughter when she starts to develop her identity. And boys may not always love dinosaurs as much as they do when they're in elementary school.
You want to avoid having to buy new curtains every time your child wants to paint their room or go with a different theme. Picking out something that is timeless and durable is important when deciding how to decorate a room for a child of any age.
First off, you should consider what kind of window treatment would be economical of space and also realistic for a child's behavior. For small children, drapes are probably not the best route to take, as too often they will be inspired to climb the curtains or yank them down, putting even the most durable fabrics through the ringer. Valances will be out of reach for a younger child, and with the right design and color palette, will stay with the room as your little one grows.
For boys, a neutral plaid valance with a color scheme that doesn't vary across the spectrum is appropriate at any age. Being too bright or playful will restrict the lifespan of the valance to your son's early adolescence – no teenager wants to have a bedroom designed for a toddler.
Also, avoid sticking to colors that are restricted to gender. A pale blue is as feminine as pink, and isn't as polarizing a color as a bright hue might be to an opinionated teen.
A classic pattern is just that because it can age well and fit into a wide range of aesthetics. A simple pattern and neutral color will adapt to a bedroom as your child grows up.