I love quesadillas! We love going to our local Mexican restaurant and fajita quesadillas are usually what we order. There are enough veggies in there to easily omit the chicken to make it vegetarian and still full of flavor. It is also easy to customize for each person's unique palate (spicy, extra cheesy, no tomato, etc). But no matter how the quesadilla is customized... the trick to getting it to taste just right is the white queso cheese. It just doesn't taste the same with any other cheese... believe me, I have tried because queso can be hard to find.
Here are some possible veggies to include in your quesadilla...
Sour cream, salsa, and guacamole are great quesadilla toppers. Yum!