If you are using an background image, consider using an background color for a default. We can’t rely on having a background image for your email, as some email clients ignore these.
Use a default background color for email clients that don’t support background images. This provides a fallback if your background image doesn’t load.
Consider using a tool like Litmus to preview what your email will look like in each email client.
Image not showing up.
Verify your image is hosted on a reachable public server (not locally).
Make sure your image source is using an absolute link, and not a relative link.