I also like peanut butter frosting ...especially with chocolate cake.
Coffee and mocha (use powdered coffee or espresso)
Rum or brandy using concentrated flavouring added to basic buttercream
Meringue buttercream with champagne used instead of water to cook the sugar
Maple (probably most popular in North America) used on spice or carrot cake
Lemon, orange, lime using true fruit oil added to buttercream (and possibly fruit curd also added)
Mango, pineapple, passionfruit using fruit puree as well as candy flavouring
Almond, pecan, hazelnut using candy flavours added to buttercream
Green tea (use matcha powder)
Cream cheese (use real full-fat)
Please--there is a world of icing flavours once you start looking in your grocery store and loloking for recipes online. I am not going to provide recipes here because I believe you need to learn to find recipes for yourself.
Look at lorannoils.com for the many candy and ice cream flavours available. They come in small size (dram=1 teaspoon) to try, for a reasonable price.
Use these drop by drop (they are very strong) but they make excellent tasting icing as well as candy.
This company also makes something called "emulsion" flavours which some people like, but I didn't care for when I tried them.
Other excellent and reputable brands are Boyajian and McCormicks (FoodClub in Canada). Buy the "natural" whenever possible.
HI i, make jodie fosters thick caramel recipe from this site. very delicious!! i add it my smbc or you can add it to any buttercream(american, etc.) Google Bobby Deens caramel cake recipe on foodnetwork.com and there would be another caramel recipe for you.
Here is bobby deens recipe for caramel cake