I'm new to cards view and really like it. I would love to see a settings page for cards would be nice. One place where we can set colors, fonts, position, visibility, and so on for the info on the cards. I'd especially like to see an option to add any/all table view column icon to cards. There is plenty of room on the cards. Somewhere is settings, have a checkbox list of icons to display on cards.
In table view, I use the following icon columns: delete, selection, select thread toggle, star, attachment, read status and spam. Reply and archive would also be nice. In cards view, for on/off icons, use contrast based on the color scheme. The others can use color to show status, just like table view.