I have made some baseball & football games over the years and I have found 24" x 24" to be a good size for a baseball field to look right for a modest size layout. And I animated the fields to have from 2 to 10 players moving on the field and on some I have put a animated scorekeeper on the elevated scoreboard.
I have also animated a football game using the Dept. 56 Football Stadium and I made the field to be 12" x 16" using the field and football players that come with the building.
The top photo is of the 1st animated baseball game which I still have and it is 35 yrs. old and has 10 animated players plus a animated scorekeeper.
Also some photos of the animated football game.
I started building my animations in 1972. & Spike's Wonderland of Animation, since 1980.