Online gallery 20x200 has a few of my favorite sports-related prints, including Tatsuro Kiuchi's "In the Ballpark" (Image 1). Also, as someone who has been a Phillies fan since before birth (just ask my mom), I am partial to Derek Erdman's original portrait of Mike Schmidt (Image 2). While jerseys are good for hardcore fans, maybe the best, least cheesy way to incorporate the sport is with baseballs themselves. Check them out displayed in Images 8, 9 and 10.
Images: Tatsuro Kiuchi for 20x200 2. Derek Erdman 3. Etsy seller ALPHABETSandINK 4. Etsy seller Fondue 5. Etsy seller Wephotoplay 6. Don Hamerman for 20x200 7. Etsy seller CheltenhamRoad 8. Michelle Drewes for Design*Sponge 9. Evan Thomas for Apartment Therapy 10. Ann Manubay and Dabney Frake for Apartment Therapy