As answered previously, Alaska'a tail logo is an eskimo. What is really interesting is that if you look at the eskimo in different liveries, the eskimo's smile has changed.
No smile: (photo taken in 1974)

Amused look: (photo taken 1991)

Medium smile (photo taken in 1979)

Current: (nearly identical to above)

The Delta question has an easy answer. Delta's new slogan is (see the DL forum & saveskymiles.com):

D Don't
E Ever
L Leave
T Things
A Alone

My favorite DL livery is the current "classic" look. The newest one looks as if a beach towel got hung up on the tail and the "old new" look with the single cheatline had nothing distinctive. I love the classic livery's double cheatline (thick blue thin red) and the slanting widget on the fuselage providing the illusion of speed. I also liked the varying sweep of the widget on the tail based upon the individual aircraft. I still don't understand why they had to soften the widget in the current livery. It seems like a waste of money to me since they had just finished updating all of the airport podiums, etc. with the "old new" design.

CWPFLY