If you can't clean up the painted edge, you could always add a 1x3 piece of wood as molding. You can even carry it up to the ceiling to frame that wallpaper. I don't see that paint color in the wallpaper, or maybe it's a lighter version of the flower centers. Maybe stencil on a design using the darker color, or another color from the wallpaper to help tie it together. Then narrow floating shelves or vertical frames or something in the painted areas it you feel you need it. Maybe turn the bed around so the wallpaper is the headboard.

Hi senba, Great suggestions above! Yes, use the wallpaper background... but keep it really,really light blue. It will keep the room homogenous and will retain the softness of your paper. That is going to be a very pretty, very fun room when complete.... please post a picture! Elizabeth Cabell, ASID, CID

There are many kinds of accent walls and when you get it right- magic. Factor in how detailed you go, as little girls change into big girls in a blink of an eye. And then you are grabbing for a paint brush again, with a dark paint on the wall- that requires lots of primer and coats of paint to cover. Give us more detail if you need more specific advice... Furniture...color scheme... Bedding... Space... Childs age....

You don't necessarily need only paintings as artwork. You can put some floating shelves near the dining space with some good crockery like plates or tea sets which can be used for occasions as well. On the wall in the living space you could keep either traditional or modern show pieces.