I'm going to try Kinnikinnick Chocolate cake mix and would like to add something to it and suggestions?~can not have dairy

Maraschino cherries are awesome in chocolate cake, so is coconut or chocolate chips. I think Enjoy Life makes a diary free chocolate chip. Raspberry preserves folded in in swirls would also be wonderful. Then you could top with decadant chocolate frosting and fresh raspberries. Yum! That sounds insanely good. Peanut butter chips (don't know if they're dairy free) would also be amazing.

What would I use for icing? What is the best way to store the cake?

My favorite trick with chocolate cake is to split the layers and spread them with seedless raspberry preserves or orange marmelade. Ice the outside with Cool Whip and garnish with fresh berries or orange slices that you split half way through and twist.

You can give Cool Whip a different taste and texture by stirirng a tbsp of sour cream into it. It gives it a taste that is richer and less sweet and a denser texture.

My brother accused me of picking up a bakery cake and saying I made it when I did this. :-)

I've done the same with an Authentic Foods Lemon Cake and lemon curd. Yum!