Hello cherylperl,
Thank you so much for using our theme AcmeBlog. This theme is designed for blog and we considered that every post contain featured image. If you didn’t use any featured image, no image available there. If you want to get rid from this, our Premium version AcmeBlog that is AcmeBlogPro have an options for setting your own default image for no image available. So, this will be the best options for you.
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Best Regards,
Acme supports