A salad mix can be as specific and as satisfying as your grandmother's favorite dish, and the components of a salad mix are as variable as your imagination allows. Chicory, mustard, cress, endive, mizuna, kale, dandelion, arugula, tatsoi; plus your choice of lettuce(s) are all options to experiment with. Even some of our "favorite" farm weeds taste great in a salad; like purslane and amaranth.
This mix will have to be lightly washed before eating to ensure that it has no grit in it. Leave it out to dry (or put it through a salad spinner) if you plan to store it in the refrigerator for more than a couple of days.