The author and illustrator Don Tate II comments on picture-book biographies on his blog, Devas T Rants and Raves!; you'll pick up some good ideas from his list.
Wilma Unlimited, a biography of the great track star Wilma Rudolph, is the first one that I want to read with my son. I still remember the song from "Wilma," a TV movie directed by Bud Greenspan: "I just want to be a Tigerbelle." Rudolph, an Olympic gold-medalist, ran for the Tennessee State Tigerbelle team in college.
Mindy at The Proper Noun bkjrnl, a new blog, reviewed Wilma Unlimited recently, too. Don't you love it when the Web works like that!
Elsewhere on his site, Don Tate posts a tribute to the late Toni Trent Parker.
Thanks to Chris at Bartography for the link to Don Tate's blog. (Is everybody in Austin writing books for children?)