FYI, Plaza (downtown) finally installing a slot card system. Not operational yet, but you can sign up at the change booths, and they will mail slot card when available.

See image below for some slot cards new to me (though they may have been out a while):

Stratosphere - new graphic
New York-New York - new graphic
Horseshoe - new design & vertical orientation
Barbary Coast - white background now
Gold Coast - blue background now
Nevada Palace - '56 T-bird graphic
Rio - larger logo now
Gold Strike & Nevada Landing (in Jean) - new graphics
Hacienda - now open near Lake Mead
Avi (near Laughlin) - red background