Yes! I recommend keeping the onion and garlic, but you can totally swap out the others. Instead of carrots, use finely chopped winter quash or pumpkin or sweet potatoes. Instead of celery, use diced bell peppers or summer squash or chopped green beans. And instead of spinach, try the same amount of chopped kale, chard, or collard leaves. Just aim for 4 or 5 cups of diced veggies (in addition to the onion), and make sure you cut them all to about the same size for even cooking.