This is a great royal icing recipe for making decorations. You can store them for a very long time (a year) in a cool, dry place. I have mine in tupperware in a closet. I made a ton of poinsettias that I can keep until Christmas.
To make 3 cups:
4 cups of confectionary sugar
3 tablespoons of meringue powder
7 tablespoons of warm water
If it is too think, add a little bit of water. Keep it covered when not in use.