I personally think frosting is the most important part of a cupcake. If the frosting is too grainy, sweet, or stale tasting...forget it!
I used a box cake mix for the Halloween cupcakes I made (pictured above), but I, of course, made the frosting from scratch.
Cream Cheese Frosting
1/4 c butter, softened
1 package cream cheese, softened
1bx (1lb) powdered sugar
Instructions: with a mixer on medium to medium/high, cream the butter and cream cheese and then slowly add the powdered sugar. I added a couple drops of food coloring to make the frosting orange.