Combine curd and liqueur in a small bowl, stirring with a whisk to blend. Add ice cream to curd mixture; stir to blend. Spoon 1/2 cup ice cream mixture into each of 4 bowls; top each with 1 crushed meringue cookie.
In a pretty dish, this is a great ending to a meal. I used it as a dessert after a Thai yellow curry with shrimp and pineapple, and it fit well. It would be good after anything hot and spicy, particularly if there's fruit involved. Also, it looks like the picture if you don't fully integrate the lemon mixture with the ice cream--just lightly stir it in, don't blend.
If you're trying to avoid the alcohol, there isn't much that can substitute for it. You could try lemonade but it is significantly sweeter and thinner than the Limoncello. Personally I would just eliminate it or add another tablespoon or two of the curd to maintain the lemony flavor and the consistency.