recipezaar#300324 has a recipe for vegan chocolate frosting. You might be able to get creative and make different flavors with it like vanilla or peanut butter.
I used to make a frosting with 1 cup milk, 1 sm. box instant (any flavor)pudding and 8oz. coolwhip... but I don't know if that will suit your needs. Whisk milk & pudding, fold in topping. Store in fridge.
I am reading a bunch of good recipes from
http://glutenfreegoddess.blogspot.comShe has some frosted cake recipes that sound good. Maybe you can make them dairy free.
Have fun experimenting!!!