Fillings can not be used as an icing for your cake. Fillings tend to be creamier and softer in consistency and are not stable enough to be used on the outside of the cake as a frosting selection. But these delicious fillings can pair well with cake flavors above and frosting flavors below to create your dream dessert combination.
All buttercream is stable enough to be used as a cake filling or frosting/icing. I use my *Vanilla Buttercream to design almost 90% of my celebration cakes as the outside frosting choice. It tends to be the best option for those piped designs and party themes that need a lot of details and icing colors (think 'kids birthday cakes'). Although the Vanilla Buttercream is often the best choice for the outside frosting.. any one of these buttercream flavors can be used as the filling of your cake (in addition to what is listed as a filling above).