Mission Control view programme icons missing. How can I get them back?
You have the "Group windows by application" option turned off – this tiles every window individually so that nothing overlaps (this is how Exposé used to work in OS X 10.5 Leopard and earlier).

When "Group windows by application" is on, the tiled windows are stacked in groups based on which application they belong to, and the application icon is overlaid on the group, as in your second screenshot.

To enable "Group windows by application", go to the Apple menu > System Preferences > Mission Control and check the box.