If the templates with an image header were rejected immediately when it was just submitted, it's normal, because templates with images as a header require an appeal for approval, our team will periodically check our approval/rejection template system to help the template get approval. Therefore, you don't have to worry if the template gets rejected the first time you submit it.
Note: Please ignore the rejected status on the dashboard. When the templates are finally approved, the status on the Multichannel dashboard will also be automatically approved.