Everyone is under the assumption that you have to use East Asian food for this...
YOU DON'T x)
Trust me, I have an American SLASH South Asian stomach and I couldn't eat sushi-etc-related-foods everyday either, that's why I make my bentos with anything we have in the fridge.
And it's perfectly possible! Just the sticky rice have to be the short grained type if you want to make bears and pokeballs, but if you use regular long-grain rice, you can still color them with cabbage and other vegetables and make designs. Carrots, Celery, Cucumubers, and tomatoes help around to make the itty bittys here and there and you don't need seaweed to make faces, you can use spinach or string beans or anything!
You just have be creative and have fun xD