I add chopped onions, garlic, grated carrots, some flour and spices to pre-soaked TVP. Onions add a bit of texture but after baking tvp densifies becoming like soft rubber.  I think mushrooms, beans, corn and peas can make it more texturized but I'm not a big fan of all those ingredients. Anything else you can think of? 
Variants of tofu skins are great for meat-like textures. If you look up chinese buddist cooking or monastery cuisine, you will find many imitated meat and poultry dishes that are often called "vegan duck roast", "vegan abalone" etc (probably by non-practising consumers). One of the best for this is dried tofu skin sticks (not promoting the seller, just a random search result for a picture). Fried tofu skins pockets and pressed tofu also work pretty well. You will need to cut them into tiny shreds or chop them up coarsely to get the effect. These ingredients have plenty of surface area and are great at taking up seasoning and sauces to mimic meat juices.  