So, here is without further ado, my room board for a teen or tween girl which is girly and fun, but not overly so:
The curtain panels, blinds, table lamp, mirror, night stand, purple blanket and wall art are all Ikea. The white headboard could be DIY. The rug was from google images, and I am not sure where to find something like this. As for the dresser - this could be easily found on craigslist and refinished. The slipper chair was also from google images.
Since this room is so very colorful, going with a neutral taupish gray would be the way to go.