Never ever use frozen yogurt or low-fat ice cream for this. The effect is simply not as impressive as with full-fat, quality ice cream. Experiment with different flavors to see what suits you.
If you like, you can make a thin glaze by mixing confectioners' sugar and water together to drizzle across the top. You can flavor the glaze with cocoa powder, to complement a chocolate ice cream, lemon juice, or anything else!