IMHO, beef and pork are sufficient. Veal and pork I use to make meatballs. With beef and lamb, add some cumin and you’ve got gyros meat.
When I make meat loaf, I like to add minced sun-dried tomatoes and maybe some smoked paprika. For the glaze, I mix ketchup with Muscovado dark brown sugar and slather it over the top of the baked loaf, then return it to the oven for another fifteen minutes or so. Pure heaven!
Lea and Perrin’s in the raw meat is mandatory. I also like to use dried onion flakes in the mix because they retain so much of the meat’s moisture.
I find panko breadcrumbs are superior to any other sort.