When my kids went to public school for a year, I did a mix of school lunches and packing lunches. They enjoyed both and got more variety. I did soups, leftover casseroles, or a hot dog in a thermos sometimes, sandwiches, wraps, quesadillas other times. I always threw in a veggie and some sort of fruit as well. I sometimes put a tiny cookie or something in as well - I wouldn't do that except that the school lunches always give them treats, so I didn't want them to prefer to eat hot lunch only because they would get treats that way. I always kept a cleaned baggie of celery and carrots in the fridge, a rubbermaid full of grapes too, so that I could easily pack lunches. Sometimes I would make pasta salad or brocolli slaw, but that definitely didn't happen daily.
Now we homeschool, but we still do similar types of lunches because I like them quick so we don't waste a lot of our day preparing lunch. We save the cooking for dinner. My 2 oldest kids are sometimes in charge of lunch - making sandwiches, quesadillas, hot dogs, grilled cheese (on the foreman grill), etc. Other days we cut up a bunch of cheese and have a big "lunchable" tray full of ham or turkey or chicken deli meat, cheeses, and a box of crackers along with a piece of fruit.