Some cake options:

Chocolate Sour Cream Cake

Yellow Butter Cake

(Lemon   Orange   Almond   Vanilla)

Blue Ribbon Carrot Cake

Some filling options:

Chocolate Mousse, Mocha Mousse, Raspberry Mousseline, 

Apricot Mousseline, Strawberry Mousseline, 

 Lemon, Lime or Tangerine Curd

The buttercream can be flavored many ways:

Vanilla, Almond,  Grand Marnier,  

Kahlua,  Lemon, Salted Caramel, Nutella

Coulis and sauces:

Raspberry Coulis, Strawberry Coulis, 

Caramel Sauce, Chocolate Sauce

 Some luscious combinations:

Lemon Raspberry Cake

Lemon Cake filled with Fresh Raspberry Mousseline

atop a swirl of Raspberry Coulis.

Kahlua Almond Cake

Almond Cake brushed with Kahlua, filled with Chocolate Mousse,

 frosted with Kahlua Buttercream

and served atop a swirl of Chocolate Sauce.

Chocolate Lovers Cake

Chocolate Sour Cream Cake filled with Mocha Mousse

and frosted with White Chocolate Buttercream.

Caramel Carrot Cake

Blue Ribbon Carrot Cake frosted with Salted Caramel Buttercream.