I wish to set the face of the Echo Area . Is there another face than the
default for this ? I browsed the C code, and have the feeling that it is
the global 'default face used for this. Can I make the default face local
to echo area ? Is there a hook called before entering echo area window ?

Perhaps should I change the face of the buffer #<buffer  *Echo Area 0*> ?

However, how can I change the face only a buffer with a given name using
face-remapping-alist ?