Since it doesn't include meat (and of course no dairy or eggs) this is a vegan dish. I don't always use the same vegetables for this curry, but I tend to go for something which could be "mashed"- squash, parsnips, potatoes etc. Because its getting cooked for a while, non-squashy food such as green beans/peppers/broccoli ends up overcooked and unappealing. The butternut squash is great in this as the sweetness makes for a tasty curry!
This isn't a fiery hot curry. I like way the aromatic spices flavour the vegetables. Having said that, if you like it hot - go for it and add chilli to taste. Amchoo powder is made of dried mango and has an interesting flavour.