There are buttons and bumper stickers (for the back of your car) with all types
of slogans for both sides.  A popular image for the pro-choice side is a wire
coat hanger and the words "never again" or "we won't go back" (that is back to
the back alley butchers).  Also a hanger with the international symbol for no (
the circle with the x across it).

Some popular slogans in the US are:  "I am Pro-Choice ( or prolife) and I
vote", "A world full of wanted children would make a world of difference",
"Pro-Family, PRo- Child, Pro-Choice" and so on.

(regarding Eric Mansoor's comment about Prolife checks, I have seen Pro Choice
checks also)

Paula Johnson
Paragon Research Associates
Seattle, WA