Here is a great recipe for icing that I tested out around halloween and it didn't disappoint.
Makes 2 3/4 cups
2 cups unsalted butter, room temperature
1 pound confectioners' sugar, sifted
1 teaspoon vanilla extract
1/8 teaspoon salt
In a mixer bowl fitted with a paddle attachment, combine butter, sugar, vanilla, and salt. Beat on high speed for 2 to 3 minutes, scraping down the sides of the bowl occasionally.
I found that it was a good idea to put the mixture in the fridge to help thicken it then before I wanted to ice my cupcakes I stirred it up to make it fluffy again.