There isn't any way I can think of to do this except to create column icons for each cover, which isn't practical.
It is possible to change the column icon processor to accept a full path to an icon file in addition to having icons in cc_icons. An advanced template would return the full path to the cover as an icon for some column.
I'm not convinced that:
- this is a good idea (performance).
- anyone but you would use it.
- iconified covers would show enough detail to be useful.
That said, I will look at it sometime next week because I'm curious to see if coding it is reasonable.