Boxed stuffing such as Stove Top, is already well seasoned and a bit on the salty side, so be sure to consider this before adding any additional seasonings such as more broth, or salty seasoning spices or mixes.
Adding in some vegetables is always a good idea and it is an easy place to "hide" some veggies for those who try to avoid them! Consider sautéing them or roasting them first.