If you want to add an image to your email invitation, you can do so by locating the 'upload image' button on the email invitation page.
To Add An Image:
Navigate to Email Communications > New Email
Find the location in the body of your email where you would like to put your image.
Click on the selected place to locate the '+' icon on the left side of the email builder
Select the 'insert image' icon
Select and insert your image