The lack of this feature is very frustrating. It's obvious that users want to decide for themselves which image is displayed as a thumbnail. I have so many cases in my notebooks where a completely unsuitable motif appears in front. How long do we have to wait and complain, Evernote, how long?
It frustrates me again and again that I can't decide for myself which image is displayed in the cardview. In particularly ugly cases I even try to get the desired image by adjusting the resolution. This really cannot be Evernote's intention that users waste time with such nonsense. Please Evernote: A small option tick in the context menu "make this the poster image"... can't be that difficult.