Welcome, and thanks for dropping by the Community. I can share details about adding logos on invoice templates in QuickBooks Online (QBO).
While you can add a logo on your invoice template in QBO, the ability to add more than one is currently unavailable. I can see how having this option would be helpful for you and your business. I recommend sending feedback directly to our product developers. They're always looking for ideas to consider on how to improve QuickBooks.
Here's how to submit feedback:
In QBO, go to the Gear icon at the top, then Feedback.