They're not just for kids rooms! I've bookmarked a couple of awesome examples of how polka dots (one of my favorite patterns) can work in a totally adult room (including the bedroom of miss Serena van der Woodsen)
My next place will most definitely have a polka dot installment.
Serena's extended polka-dot headboard and wall hanging
bathroom with perfectly oversized black polka dot wallpaper
allover polka dots...
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(click on images for sources)