Layered hair bows are probably the most popular type of bows. You might often here them called stacked as well, since that is pretty much what they are. Layers of ribbon stacked on top of each other to make a large and beautiful hairbow.
Here are some options for layers besides just using a bow as the base for it:
* Add smaller bows attached to the main bow loops
* Spikes or sprays (you can have multiple layers of these!)
* Loops that surround the loops of your main bow
* Korker ribbon embellishment center
* Another bow of a different style or size
Here are some layered hair bows as examples: