Depends how fussy he is! I find lunchboxes much harder to do for DD as she doesn't like cheese, butter or mayo so sandwich fillings are really dry! DS on the other hand will eat just about anything savoury but is fussy when it comes to cakes, etc.
Some of the things we do:
Pasta / Couscous / rice salad
Different bread: wraps, pittas, rolls, bagel, etc
Sandwich fillings: cheese, tuna, hoummous, sardines, tinned salmon, soft cheese, marmite, egg mayo, chicken & mayo, peanut butter etc
Crackers & nibbly bits (cheese, ham etc)
Banana bread / banana muffin
Flapjack
Various fruit / fruit salad
Chopped cucumber & carrot
Jelly / Rice pudding / Custard as a change from yoghurt / fromage frais
Drink: water / smoothie / fruit juice / very occasional milkshake in a carton!
I'm trying to vary their lunchbox a bit more again as towards the end of last term it was pretty much the same thing every day!