The Williamstown Theater Festival has announced casting for the upcoming summer season.Randy Graff and David Schramm will play Mrs. and Mr. Peachum, and Karen Ziemba will be Lucy Brown, in “The Threepenny Opera” at Williamstown this summer. They join Jesse L. Martin, Betty Buckley and Melissa Errico in Peter Hunt’s production. Lili Taylor has been set for Michael Greif’s production of “Landscape of the Body,” by John Guare. Also starring are Michael Gaston, Sherie Rene Scott and Jose Zuniga. Dana Ivey, Becky Ann Baker and Kristine Nielsen will appear in Dylan Thomas’ “Under Milk Wood.” Darko Tresnjak directs. John Michael Higgins will play tennis star Bill Tilden in A.R. Gurney’s “Big Bill,” alongside his wife, Maggie Welsh. Mark Lamos is newly set to direct the play.