1) Think about your favorite ice cream flavors, desserts, candy, cocktails, fruits, spices...
2) Think about how those would be as ice cream and write a list; like "violet ice cream with candied violets and dried strawberries, striped with violet syrup"
3) Get a list of all existing ice cream flavors
4) Remove from your list all the existing ice creams
5) start experimenting.
Take some good vanilla ice cream and let it soften so that you can mix in different flavors.
You can get quite a lot of different flavors with essences, spices etc.
You can create ripple with sauces, syrups, jams and jellies.
You can make sorbet and mix with ice cream.
You can mix in pieces of fruit, cookies, candy. Dried edible flowers, nuts and almonds..
More ideas for flavor experimenting
What would your favorite flower be if it was ice cream?
What would your favorite animal be if it was ice cream?
How could you change your favorite ice cream to make it even better?
You could get ideas from this list: You Will Not Believe These Weird Ice Cream Flavors From All Over The World!
Or you could go all Japanese and create ice cream flavor no-one would ever eat - except the Japanese...