I followed the beginner steps for creating a child theme. The child theme was created and it appears as an option on my Themes page. But unlike the other Themes on the page (including its parent), there is no preview. The other themes ("Twenty Twelve," "Twenty Thirteen," and "Twenty Fourteen") are all listed with an image preview. My child theme ("Twenty Fourteen Child") does not have any image. The child theme can be applied without issue.
This issue arises when I create child themes from other themes as well. Any ideas why this is happening and if I can resolve?