Quiche is a food idea that has been around for a very long time.
Of course the French claim to have been the first to combine eggs and cream in a pastry crust, but it is not worth the argument to disagree.
The most well-known variety is most likely quiche Lorraine, named after a north eastern region in France, dangerously close to Germany, whose people make a great quiche with onions and bacon, known there as zwiebelkuchen.
The basic ingredients are the crust and the egg and cream custard. It would be difficult to deviate from that base, but just about anything else you might like to add will work.
Think of asparagus, roasted red bell pepper, shrimp or mussels, almost any cheese that melts well, and almost any fatty pork, such as bacon, ham or sausage.
Here's a simple quiche recipe that is pretty darned good.
QUICK AND SIMPLE QUICHE
1 frozen pie crust
2 large eggs
2 egg yolks
1 1/4 cups heavy cream
Salt and pepper
2/3 cup chopped ham
2-3 cloves garlic
1 cup freshly grated Gruyere cheese
Optional, 1-2 pinches nutmeg
Preheat oven to the temperature indicated on pie crust instructions. Beat the eggs and yolks until smooth, add the cream and beat again, then season. Add the ham and cheese, give it a good stir, then pour into the crust. Bake until the custard is firm and the crust browned. Serve hot or cold. Serve this quiche with a dry Riesling, not a sweet wine.