OK, here's the final missing ballpark from Garlon's expanded list: The OG
Polo Grounds. The short version of the name is that it in fact belonged to a polo club who had, of all things, been evicted from their previous home by a baseball team. This plot of land across the street from the northern edge of Central Park was enclosed by the polo club, then rented out for use by the independent New York Metropolitans. The Metropolitans joined the AA at the same time the Gothams/Giants were created (by the owners of the Mets) to join the NL, and both teams shared the grounds. Eventually, NYC plowed the street grid through the grounds with little warning, and when the Giants founds themselves in their new permanent digs, that got called the Polo Grounds out of habit.
See more here.
Google Drive link to the Polo Grounds 1882-1888
There was more info than I was anticipating, including a couple of photos. The artists' depictions of the grandstand were inconsistent, I ended up making reminiscent the Sportsman's Park model. I also put ads up on the right field wall behind the crowd, inspired by the photos that are out there. I found a mention of the right field line being 300 feet, so I went with that. The other dimensions are educated guesses, and I made it symmetrical out of convenience as much as anything else. The background and trees probably make it a bit more rural looking than it was, but hopefully it's close enough. I went for a roughly 1885-1886 appearance, when permanent walls went up and the photos were taken.
As I've said elsewhere in this thread, I intend to keep adding to things here, and I encourage others to do so as well! I will likely be scarce through the rest of 2024, so I'd like to wish everyone here happy holidays (no matter which ones you do or don't celebrate) and a wonderful 2025.