The separate cover file should follow these rules:
Only JPG, PNG, and TIF images are supported.
The image width must be at least 1400 px. Your cover may be larger. It should be about 1.6 times tall as it is wide.
Portrait (vertical) rectangular artwork - no squares or horizontal covers please.
Please do not list URLs, email addresses, or social media user names on your cover art.
Your image should use RGB color (not CMYK).
Your image should be at least 72 dpi but we recommend 300dpi.
This is the one!