You can customize the buyer's Home Screen. When they log in they will see the welcome image as well as the branding colors that you select.
Go to Settings -> Company Profile -> Branding
Load an image in the Buyers Home Screen section
Recommended Image size is 1920 x 1080 pixels (jpg, gif or png)
Select primary and secondary colors for the main menu appearance across the top bar throughout all the screens.
Settings will take effect immediately.