Mozzarella or Muenster cheese can be used in place of the Swiss cheese. All of these cheeses melt nicely and have mild flavors that go well with mushrooms.
A variety of exotic mushrooms are available in supermarket produce departments. Try cremini, shiitake or chanterelle mushrooms in place of the common white mushrooms.
Use 1 tablespoon chopped fresh herbs, such as basil, oregano, marjoram, chives or parsley, in place of the dried Italian seasoning.