You can add your own image to your campaign at the Content Template stage of the campaign set up flow.

Click on Upload Files. You can select an image from your computer, drag and drop or copy and paste.

Choose a high resolution image. Boma will automatically resize images to fit perfectly in the digital channels you have selected.

Further Reading:

How do I search for images in BOMA's image library?

Why won't my image file upload?

My Facebook post image isn't the same as the one I want

Link and image Previews on Social Media (Open Graph Tags)