When setting up a bulk email template for emailing, you can either "attach" the images used in your template with the email (would need programming), refer to an external site that hosts your images (would need client to have internet connection, and some clients block these as usually caused by spam).

The better way is to embed the images inline:

In Seamonkey, when you have your html template open, to set up a background image go to Format->Page Colors and Background:

{{attachment:Screenshot from 2021-07-07 14-12-19.png|Screenshot from 2021-07-07 14-12-19.png}}

Click on "Choose File" and choose the file you want for your background. Click on "OK"

{{attachment:Screenshot from 2021-07-07 14-03-21.png|Screenshot from 2021-07-07 14-03-21.png}}

To insert an image, put your cursor where you want to add the image and go to Insert->Image

{{attachment:Screenshot from 2021-07-07 14-06-21.png|Screenshot from 2021-07-07 14-06-21.png}}

click on "choose file"

You should see a view of how the background and image look. At this point the '''background is automatically converted to in-line html, however images need the file to be available locally.'''  This will cause a problem when you email the template.

To fix this, open a new instance of seamonkey go to Format->Page Colors and Background. Click on "choose file" and choose the '''image you wanted to insert (not the background)'''. Click on "OK". Go back to Format->Page Colors and Background. Your image is now converted to inline graphics. Select the whole "background image" field and copy all the text inside (this is the data for your graphic)

{{attachment:Screenshot from 2021-07-07 14-23-50.png|Screenshot from 2021-07-07 14-23-50.png}}

you can now close the 2nd instance of seamonkey.

Go back to your first instance, right click on your inserted image and select "image properties". Paste your copied text over the "image location" field. Your image is now inline.  If you send the template as bulk email, it should have all the graphics intact.