for a photo-op try the sample gates at Kirkwood and Indiana on the edge of campus, tons of great food, one food doesn’t pop into mind though,
for bars, go to Nick’s on Kirkwood and play a game of Sink the Biz; ask the waitress

I agree with the others. Nick’s is the classic IU bar, but also check out Kilroys and Upstairs Pub, both of which are close to Nick’s and the Sample Gates. Kilroy’s Sports is a few blocks away. I would also recommend the Irish Lion, just southwest of the courthouse square. The stretch of Kirkwood from the Sample Gates west to the courthouse, the courthouse square, and Walnut Street north to about 7th Street constitute the main college town strip. It sounds like you will have great weather for just walking around.

For tailgating, the liveliest area will be in the wooded area immediately south of the stadium. There is tailgating in all of the parking lots, but the area south of the stadium is “the scene,” if that’s what you are looking for. Get there reasonably early. You wouldn’t know it from our attendance, but tailgating is a pretty big thing at IU.