Part of the iconography of the Grateful Dead, the Steal Your Face
is a humanoid skull with a circle in place of the cranium.
The circle is split by a white lightning bolt with the remaining space
in the circle filled in with pure red and blue on the left and right
sides, respectively. The logo was designed by Bob Thomas with help from
Stanley "Bear" Owsley in 1969, primarily to spray paint on
the band's equipment to keep their gear from getting mixed up with that of
other bands. Variants on this design are legion (and
are probably unauthorized), with another common design
being the Space Your Face -- the circle filled with a star field;
"space" often refers to the free-form, instrumental interlude the
band usually took during their concerts, but could also symbolize
transcendence.
The phrase "steal your face" actually comes from the
Jerry Garcia/Robert Hunter song "He's Gone":
Like I told you,
What I said...
Steal your face
Right off your head!
The lyric refers to Lenny Hart, Mickey Hart's father and the band's manager, who is suspected of embezzling money from the band and disappearing.
Sources: Bear's website at http://www.thebear.org, and
my copy of The Grateful Dead's Europe '72 Disc One.
He's Gone lyrics by Robert Hunter, music by Jerry Garcia, copyright Ice Nine Publishing Company, Inc.