[Ken Maltby]

@myki;
I did try the couple of .mobi files that I had on my AuraHD, and my default sleepcover is what was used for those files. The cover of the .epub version of the same ebook, is used as the sleepcover.

@church mouse;

The recent versions of Koreader have a "Screensaver" menu item, in the Reader menu. It has two options: "Use this book's cover as screensaver" and "Display proportional cover image in screensaver" You can have both options checked if you want. I guess you would want to uncheck the first one, for the book or books that you do not wish to use the cover. With it unchecked, the default image file that you point to in the advanced settings will be used. If you don't specify an image file to use, when the book's cover is not there or not found or not to be used. The little "Suspended..." msg box will be used.

Luck;
Ken