One of the most difficult things to pull off in a room is to mix patterns. When done successfully, you get visual interest but not distracting busyness.
We like the mixed patterns in this child's room designed by Robert Passal. The room sports a bold checked black and white wallpaper, polka dot blinds, a block quilt, patterned pillow, and a striped rug. But it all works together mainly because the color palette is kept simple. The main colors in the room are blue and green while the checked wallpaper, although bold, is a neutral black and white. To see more examples of childrens' rooms with mixed patterns, check out Robert Passal's portfolio.
Mixing Patterns Successfully
(Image: Robert Passal via Little Green Notebook)