There are 2 things you can do:
You can use Facebook’s Debug Tool. Copy the squeeze page link that isn’t pulling an image and paste it into the debug tool and click the “Debug” button. Then paste the link into a new Facebook post. Most times the image will appear when you try posting it to Facebook after using the Debug Tool.
You could also upload your own image. To do this, paste the squeeze page link, then click on the “x” to remove the grayed out image and upload your own image.