I ran across this website that helps those who don’t have MLB 19 get an idea of the different stadiums that will be available. Can’t guarantee it’s 100% accurate but seems to be pretty dang solid. Great resource to start making ideas for your rebrands.
http://baseballsimulator.com/bp/
Includes the MLB stadiums, Minor League, Classic, Spring Training. Has dimensions and a photo showing the parks (The photos seem to be from 2017).
What stadiums are you planning to use for your rebrands?