It's really up to you weather or not you want to add nuts or raisuns.  If I make this for a party where someone coul have a nut allergy or for kids who may be a little picky, then I just leave it plain.  If I know that the people I'm sharing it with like nuts and raisins, then I add them.  About 1/2 cup of chopped walnuts add a lot to the flavor and texture of the cake.  You can also add a few more to sprinkle on top to help decorate the cake.