This is the bumper sticker I have on the back of my car:
I ordered a number of them around a year and a half ago. I believe it was from this site.
I put it right up above the tail light on the trunk hatch, so it's good and visible. I figure down on the bumper is too out of the way. Once and a while when I'm at a red light I'll pop a glance in the rearview. The expressions are various.
Having a Divine Mercy bumper sticker is more than just stating that you're Christian through kitsch; far more. To the person who sees it, the image does not direct their attention to me as a Christian - because the image is directed at them.
"By means of this image I shall be granting many graces to souls, so let every soul have access to it." (#570) St. Faustina diary.