DeviantART has produced some more Mail Stamp icons for people who are tired of looking at the Red-tailed Hawk all day.
The first set 
is European and avant-garde.
The Mail.app icon is not a stamp and the icon provided for Entourage is.
Of course, you can use the Entourage one for Mail.app if the soft candy-pink look appeals:
The second set is also European but more traditional. It is a collection of six Springtime stamps — a sunset and sunrise in India, an orchid, cherry blossom, magnolia and some kind of pretty purple plant:
Changing the Mail.app’s icon is easy. Hawk Wings maintains a list of over 200 alternate stamp icons for Mail.app, so you are spoilt for choice.
