One of the fun things to do to with one of my ballparks is add accessories to them. My ballparks are very close to N or HO scale model railroad items. The seated patrons at my games are HO scale model railroad people. Depending on your budget and patience, you could order cheap bulk lots from China/Japan, or, if you like quality, you can order some of the many different Preiser or Woodland Scenic sets to add a sense of realism to your ballpark.
Some of the more interesting ones I have seen include: an ice cream man, clowns, kids on bikes, parents and kids holding hands, kids playing baseball…etc.