I made this banner to put above my son's crib. However, it can easily be altered to be used as a birthday or holiday decoration. Using coordinated fabrics and quilt binding, I managed to finish this in an evening.
I cut out triangles that were 6" tall and 5" wide and spaced them 2 1/4" apart. I laid them out on the floor before sewing them to make sure the colors looked good together when doubled back.
An alternative to using fabric would be using scrapbook paper and embellishments to create something just as lovely. Add stars, letters or other symbols to each flag to personalize it. Use bold contrasting colors like black and white with pink lettering for an edgier look. Have fun!