Hold picture day on opening day, schedule each team's pictures about 2-3 hours before their game.
This way you have people (families) there for...
Vendors - clothes, jewelry, etc (especially sports-related items.) (charge them to be there?)
Radio Station remote (maybe have a local sporting goods store pay for the remote in return for letting the store set up a booth.)
Equipment Exchange - families donate their outgrown equipment, and the league can either give it to others or sell it for $5 per item (not bad for cleats, a glove, a bat, etc!)l
Bounce Houses
Hitting contest (have the photographer or other vendor(s) pay for some prizes for different age groups/ boys/ girls.)
Local BBQ shacks often have set ups for selling food at events, have them come & you could charge them a flat fee or percent of sales to be there.
Petting Zoo
Climbing wall - if they charge people to participate, then you can charge them to come to your well-attended event if you want!
Cake Walks
The more inter-active fun things you have, the more people will stick around. But the key is that the team picture day gets everybody there!
Good Luck!!