Cold meatloaf is great with anything. For instance, roasted red pepper, lettuce and a drizzle of extra virgin olive oil. Or kraut and mustard. Or with a dollop of cold mashed. Sometimes I’ll put a slice of salami or ham on it. Amost any kind of cheese will work too. As far as condiments goes just keep a variety in the fridge, and try out new choices. When the garden is full theres no telling what will end up on it. Be creative. There are a gazillion ways to make a meatloaf sandwich. Try not to make it the same way twice.