Do you mean main course dishes or sides? For sides, we love chargrilling greens and serving with tahini/lemon/oil/yoghurt dressing or creating a lemon/honey/garlic dressing.
Stir fried veg work well with a lot of proteins and you can use a ready made sauce or we usually just add lime juice and soy sauce.
I sometimes make "warm" salsa but grililng/frying peppers, tomatoes and chilli and then chopping them up with some oil and sherry vinegar.
Rice based dishes work well as sides or mains - risotto, pilafs etc - and you can add all kinds of vegetables to those.
Roasted veg is something we do often as a main - roasted tomatoes with burette or goats cheese on spaghetti; roasted meditteranean vegetables with flat breads and humous; roasted cauliflower served with a pilaf of some sort etc.
Vegetable curries and soups are also good options for vegetarian meals. I do a lovely Thai style red curry with butternut, mange tout and tomato. I've also done a similar one with aubergine and cauliflower. I'm keen to try make a version of brinjal bhaji too.
Pasta dishes that are veg based work well too. two of our favourites are tomato, aubergine and chilli topped with feta cheese or spinach, ricotta, lemon and garlic.