My mom has one. It's a flower that uses my dad's name to make the petals and two leaves, one made from my name and one made from my sister's name. She got it a few years ago, after she'd been married and had kids for awhile.
My aunts and some of my friend's mothers also have them, and almost all of them are references to their children.
My Irish friend has a Celtic knot on her lower back, which she got before moving to America, and my Catholic friend has a really detailed cross.
The only time I've ever seen a lower back tattoo and thought it was bad was when I saw a girl who had her own name tattooed on her lower back in this font: link (same color and she had included drawn on sparkles). My first thought was "Is that so he knows what name to call out when he finishes?"
Other than something that insane, I don't see why they're called tramp stamps.