Mustard is one of those ingredients that I personally use on just about everything. Mustard seed has almost become the bacon of spices, for me!
In terms of salad, adding a mixture of homemade mayonnaise with some nice mustard is a great way to add some fat and flavor to some nutrient rich greens! Add a dollop to the top of some green beans. Dip some fried chicken fingers into it and call it a snack. This is a quick and easy flavor enhancer!
In the case of this recipe, I've left a very basic ratio. However, it's delicious with some freshly chopped rosemary or thyme. Adding a tablespoon of sugar free honey can bring a nice sweet quality to it. Adding a tablespoon of apple cider vinegar will bring it some tart. Play with it and see what you come up with!