Tips for a girl's room:

Stars Starlight is a great theme, and you'll find many fabrics, wallpapers, and bedding with star patterns. This theme appeals to both boys and girls, and is available in many colors both bright and pastel. Wonderful theme pieces can be the "star" in a room. You might get star-shaped rubber stamps (or sponges) and dip into wall paint to create your own starborder, decorate furniture, or make random stars all over the walls or ceiling. A star quilt or rug will complete the theme.
Moonlight Create a wonderful, soft look with by the light of the moon. The ceiling might be midnight blue, with painted moon and stars, or use some of the stick-on glow-in-the-dark stars. Embellish a colorful painted bookshelf with crisp white stars, or liven up a plain white chest with a rainbow of star shapes. Find a moon and star quilt or fabric to use for window treatments. Then add a moon cutout headboard.
Angels, Fairies, and Elves This universal theme will be adored by girls of any age. Angel themes could use faux painted skies and clouds, fluffy canopy beds, and soft icy pinks, blues, and lavendars. Fairy shapes are appealing with transparent wings, sparkling wands, and silvery magic dust. Try to incorporate some sparkles with glittering accents, silver paint, and magical designs.
Flower Power Bright and bold oranges, sun yellows, lime greens, and watermelon pinks are the basis of this retro-60's look. Find colorful borders and fabrics featuring stylized simple flower shapes in hot colors, and match these with some plain fabrics for ruffles, valances, and window seat pillows. These flower shapes would be easy to enlarge on a copy machine and trace onto the walls in random patterns, then paint with wild colors matched to the fabrics.
Sunshine Paint a mural of hills, with the sunrise peeking over the top. Use sunny yellow checked bedding and quilts, green rugs for grass, and paint the ceiling a soft sky blue. Waking up will be easy and fun using this summery look which is sure to please many a young child.