As I've read this thread I see many have strong opinions on both sides so I won't belabor the point too much but, yes I think providing additional visual clues at the notebook overview object would be nice to have. There are many ways to view and organize notebooks but for myself working with a number of external companies I would love you use their brand logo as the cover to more quickly jump between active projects. While I understand there are technical commitments to this ask I think starting with a minimal approach of native color/gradient options would be a reasonable starting point with minimal work. The concern of syncing between experiences, i.e. mobile and desktop, I think it is being overstated. Clearly Evernote has the ability to sync between devices and user accounts as they have proven with their shared notebooks and cohesive experience with files and images attached to notes. This would be an extension of existing capabilities so I do think this could be implemented fairly easily.