For extra flavor, you can sauté chopped celery, carrots, or mushrooms with the onions before adding the TVP.
A splash of hot sauce or vegetarian Worcestershire sauce can add a nice depth of flavor.
Whole canned tomatoes, pureed by hand or in a blender, often provide a better texture than pre-chopped ones.
Homemade breadcrumbs from toasted whole wheat bread work well, but store-bought or cracker crumbs are also acceptable.
This recipe scales well for two loaves, but do not attempt to make a single larger loaf as it may not cook through evenly.