Two ballparks remain for Milwaukee: the Milwaukee Base Ball Grounds (sometimes called Eclipse Park), home to the NL team of 1878, and the Wright Street Grounds, home to the Union Association team of 1884. Both of these teams were one-year affairs, and the
Union Association Brewers were more like a one-month affair--the team joined the UA along with the St. Paul team as the Chicago/Pittsburgh and Wilmington teams dropped out. There are
some details to be found about the UA ballpark, and the size of the lot the NL park sat on is out there as well. I decided to make a hybrid of the parks, with a ballpark kind of like the text description of Wright Street put onto a lot kind of like the NL park and oriented to provide a reasonable* outfield.
Since this park didn't really exist, I gave it a name that reflects its origin: "Milwaukee National Union Grounds". Naturally, you can rename it whatever you like in the game! I have the field markings set to 1878 rather than 1884, since the UA Brewers only had 12 home games compared to 25 home games for the UA Grays in 1878. I also made the park gray to reflect the team name.
Google Drive link to Milwaukee National Union Grounds
Not too much to add here, I think? The screenshots below are all of the model, since there really are no depictions of the park out there. Not sure what I'll try next--I may try grinding away after the remaining NL parks, or may try the remaining DC parks (both from 1884 and I may try a similar hybrid approach for those)...