I guess it depends very much on what kind of sausage you use. As a broad generalisation, Spanish sausage uses a lot of paprika/pimentón and garlic; Italian sausage, garlic, fennel,maybe peperoncini, maybe basil; British sausages use a lot of sage and thyme; German sausage might use caraway, nutmeg, allspice, bay leaves. It´s just a question of experimenting, I´d say.