Hi sabina-outsidega,
There are 3 sizes of logos in our built-in templates. S, M and L. Please refer to article below for settings:
Add, customise, or remove logos on sales forms
If you require your logo to be bigger than the L size, I would suggest creating your own invoice template and uploading it to QuickBooks. Here are some steps you can follow found in link below:
Import custom form styles for invoices or estimates
I hope this helps you, reach back out to us if you needed any further assistance.
Kristian.