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.
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
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 and have access to its administration, there are two ways how to improve image posting:
1. You have to make sure your pages are formatted the right way.
Here is the instruction from Facebook on how to set up pages' metadata so it pulls the correct image from your pages:https://developers.facebook.com/docs/sharing/webmasters/getting-started/basic-link/
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:
https://developers.facebook.com/docs/sharing/webmasters/images
2. Another way is to verify your ownership of the domain name of your feed. Here are the instructions:
https://developers.facebook.com/docs/sharing/domain-verificationIn this case, we will be able to take images from your feed and attach them to your Facebook posts correctly.
However, you need to make sure that all images are linked to your verified domain. That means that all of your images have to be hosted on this same domain but not on a third-party domain like a cloud server or CDN.
Unfortunately, there is not much we can do about image attachments to Facebook posts. Hopefully, Facebook will lift these restrictions sometime soon.