You don't say if it's a finger buffet, or just a help yourself.
I'd agree about hummus style dips (I often use the cheaper butter beans).
Veg chilli is great and I 'cheat' by using the cans of kidney beans in chilli sauce. You can wrap in tortillas or similar if you like.
Also - take some chick peas (can, or boil them up yourself) and roast with oil and salt and some flavouring - chilli or soy - whatever - they add crunch and taste. They last ages, so easy to do in advance.
I often do mushrooms a la greque, usually served as a salad, but can be served warm.
One of my great favourites is to halve, stuff and bake a butternut squash - it takes ages but if you make it lovely and soft, folk can just scoop some out.
Baba ghanoush is a great favourite (though not with me - I never get it tasty enough!
I love to make a roulade with creamy cheese like boursin and fill with spinach, but it is a last-minute fiddle, so I don't usually do it for a crowd.
Little tarts or mini pizzas are easy - you don't have to put cheese on them. I make the cases in mini tart tins and freeze ahead.
Of course, you can get vegan 'cheese', but I don't usually. Tomato and olive make a lovely filling.
You have lots of ideas now, hope some of them work for you!