You will have a default account level background image that can be used on all proposals automatically. You can over ride this in each template to set a new background per template. You can even override the template background image in each individual proposal. This guide shows you how.
To upload a new background picture while creating a proposal or editing a proposal template follow these steps:
Press the Select background icon. It looks like this:
Press Upload background (or select from backgrounds uploaded earlier)
Select the image you want to use by choosing from a local file, direct link etc.
Press Add.
Done 👍
Remember! You can upload images or mp4 files.