That could be quite useful if Calibre had a few of these Default covers, and gave us access to them, to replace them with our own PNG, then we could have a nice image with transparancy, which would work in all instances - But I guess thats asking for something only a few would want.
Ok, working with what we have got, yes I think I'll go with black BG but am worried that in future caliber may change to a white coverflow BG and mess up all our book covers. Don't really feel like going through 14G books and redoing them.... so I may just go with a flat image.
I seem to have a quite a few short stories, novellas and aritcles that have no generic cover, despite much searching, and can do wonders in PS so making my own is no problem. You do have a nice idea with your genres though.
Thanks for the reply, will keep this on the back burner while I ponder.