The great thing about this form factor is that you can put just about anything you want on top of the sushi rice, so you're not limited to things that will fit within a roll. I've made sushi bowls topped with everything from steak to spicy tuna to poke. In terms of veggies, you can add pretty much anything that you might add to a salad. The key is to include a variety of tastes, textures, and colors.