[Nakishee]

I think you should just improvise, then, let the creative juices flow ;-]
I love kyaraben and charaben, and often times I'll just leave meat out and replace with spicy tofu or omelet.

As for fillings and toppings, I use shredded/chopped veggies like carrots or peppers.
Maybe you could experiment a bit, lol, find out what looks the cutest and tastes the best