My daughter has a packed lunch as like you say it's easier to carb count. Here are some ideas of what she has in her lunchbox.
Cream crackers (Jess likes them with margarine and marmite)
Cherry tomatoes
Cheese - babybels, lil' moos or cheese strings
Yoghurt
Cereal bars
Popcorn
Salad of sliced mixed peppers, cucumbers, carrots, olives, feta cheese
Cesar salad topped with a few croutons (you can add chicken or some bacon bits)
Blueberry muffin
Sugar free jelly
Fruit salad - lots of melon and berries, just a few grapes
Low sugar tinned sweetcorn
Cold meats - chicken drumsticks
Pasta salad
Rice salad
Chicken balls
Slices of spanish omelette
Ham, cheese and tomato sticks (like mini kebabs threaded onto drinking straws)
Cocktail sausages wrapped in bacon
Mini sausage rolls
Quiche
Leftover cold roast potatoes
Potato salad (we make ours with boiled pots, hard boiled egg and mayonnaise)
We add a treat occasionally, usually something small like a kinder chocolate bar or a happy hippo.
As a side note we use a lunch box by Lock & Lock that is square in shape and has four little dividing compartments which is ideal for keeping all the food items separate. Also Laptop Lunches make natty little lunchboxes that work a treat for keeping your packed lunch organised.