Honestly, table runners can be used on/for anything you want. The same goes for almost all decorative fabrics (table cloths, lose fabrics, etc.). You are only limited by your imagination.
Just know that table runners are only called table runners because that is what they are made for. This doesn't mean you can’t use it for something else. The same principle goes for all decorative pieces, and using something for a completely irrelevant purpose is also known as innovation (as long as it works of course). So again, you are only limited by your imagination.