If you use the option "Use item's images and videos" in the Advanced campaign settings, most likely your original content doesn't have any images. That's why you don't see any images in your post. But first of all, you have to verify the domain ownership to be able to use images from it.
If you are not using "Use item's images and videos" in the Advanced campaign settings, the Facebook bot fetches the image from the original content. It usually takes the image from metadata tags. And if the original content pages are not well-formatted, or formatted in a way that Facebook can't fetch the correct data, you may see "strange" images in your Facebook posts.
If you own the original content website or can edit it, there is an instruction from Facebook on how to set up pages' metadata so it's bot could pull the correct image from your pages.
Facebook suggests specifying image links in metadata tags of your website pages like this:
<meta property="og:image" content="your_image_url">
Also, check the Facebook requirements to post images.
Incorrect or no photo at all in my Facebook posts
Media content posts to Facebook
David Logan
Updated 4 months ago
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