Kosko began his film art career as a set draftsman on George A. Romero's 1985 zombie thriller, Day of the Dead (starring Sherman Howard). He later worked as property master on another Romero film, 1988's Monkey Shines (starring Stephen Root). Kosko has since been an art director or assistant art director on such films as The Silence of the Lambs, Lorenzo's Oil, Bob Roberts (featuring Lee Arenberg and Ray Wise), Cool Runnings, Philadelphia, Kingpin, The Devil's Advocate, Paramount's Deep Impact (featuring James Cromwell, Denise Crosby, Christopher Darga, Mark Moses, Tucker Smallwood, Kurtwood Smith and Concetta Tomei).