The flags are mainly from Flags of War. These are a total lifesaver, as I wasn't relishing the prospect of painting more flags (the larger Paraguayan flag is one that I painted 6 years ago, and which got nibbled the other week by our cat, Millie) and I was having problems with the flags uploaded on the Perry website. Flags of War also do lance pennants in any colour you want. The palm trees and broken walls in the photos are all scenic bits I made for Frostgrave: Ghost Archipelago last year; I think they look ok-ish for South America.
My immediate plan is to get to 10 infantry units per side (perhaps a couple more on the Allied side to reflect the three different contingents), a bit of cavalry and then take stock. All infantry units will be between 18 and 24 figures and cavalry units will be 12 figures. That's not particularly historic, but provides a manageable set-up. I'll post about these units separately in due course, and will start with the original one again as I added more figures to it.