This headband is made using a picot fan stitch and also woven stitch (also known as linen stitch). Woven stitch is nice and stretchy and provides the elasticity.
This was made to fit a 1-year old but you can easily adjust to fit by adding extra rows of the woven stitch or by adding in more picot fans (if you are making for an adult). Instructions included.
The best bit is this is a quick make and can be made using any dk stash yarn you may have to use up.
How about adding beads to make this tiara fit for a princess?
Debbie Bliss Prima (or any double knit yarn)
Project shown measures 16 inches unstretched, 19 inches stretched. Size easily adjustable for an older child or adult.
You can find this pattern along with many more at Make My Day Creative: