I know there are some classics like oil and vinegar, but when it comes down to it, actually a lot of foods can work as salad dressing.
One simple dressing I make is a lazy peanut sauce: peanut butter, some sweet chili sauce, and a bit of hot water. Toss a few peanuts onto your leaves and it's pretty solid.
But I've gone a lot further. If you have leftover soup or chili, that usually works pretty well. But you can also use pretty much any curry or really any stir fry. If there are big chunks, like a strip of seitan, you can either live with it, or spread it on a cutting board and chop chop chop before you toss it with the leaves.
As for the leaves, my preference is something sturdy like finely shredded green cabbage or romaine.
I know this post is a bit odd, not being a recipe. I just wanted to share that when it comes to salad, it's easy to be creative if you get out of the traditional salad mindset.