Glad to have you here in the Community. At the moment, only a Company Logo is supported on invoices at this time. I can see how this would be valuable to not only your business but to others, as well, so I'll submit this idea to our Product Development Team for review.
In the meantime, I recommend keeping an eye out on our blog to stay up-to-date on all things QuickBooks.
If you have any other questions, I'll be here to help. Have a wonderful week!