You have the option to customize the email footer so that your preferred signature appears in the email sent (to join Zapty) to guests, members. Here is a one time setup that you need to do. Under the Branding tab in Organization settings; you can create your custom email footer that appears in the email.
This option is available if you have subscribed to the Enterprise plan.
Type out the footer text
And for inserting the image use the image option in the editor; paste the URL for the image. Optionally provide dimensions and then click Insert.
The invitation email sent out will have the footer as shown below.
Zooming in on footer for clarity.