Salmon BBQ's very well. We tend to marinade either with Cajun spices or tandoori. I then use either a metal BBQ basket or skewers to do peppers and onions to go with it (courgette and mushrooms sometimes too), with a little of the same marinade.
I know you said you're bored of chicken but I do the same thing with chicken but serve with little wraps/tortillas for variety.
Ribs are nice for a change too. Used to be a BBQ staple but not so common now.
Prawns would happily take the same treatment, on skewers with the veg.
Halloumi is fab on a BBQ too. Thickish slices and you don't need to do anything special to them if you don't want.
Giant field mushrooms stuffed with cream cheese (flavoured if you want) BBQ well.
I also do the thin cut minute steaks sometimes. Marinade in a bit of garlic oil and well peppered, they cook so fast and are really tasty.
I always want potatoes with a BBQ so when pushed for time I just do buttery new potatoes but you can fling those on the BBQ for a few minutes once they're done for a change in flavour. Or I do a potato salad (potato and eggs tossed with 50/50 mayo and natural yogurt as the base). You can add all sorts to it depending on your family tastes.
A tomato based pasta salad can be nice for a change too.