Development on Puss in Boots: The Last Wish had already started in 2012, with Guillermo del Toro mentioning that a few drafts had already been completed. It was officially announced under the title Puss in Boots 2: Nine Lives and Forty Thieves in July 2014.
It then received a full rewrite in 2015, and finally retitled itself as Puss in Boots: The Last Wish in 2020.
The film went through a lot of other changes - the main ones being a lot of director switches (including Bob Persichetti, director of Spider-Man: Into the Spider-Verse, between 2019 and 2021) and a few scrapped characters like Don Manolo (a villainous shoe cobbler).
Personally, one of my favourite ideas which was obviously toyed around with is the pink feather on Puss's hat! (You can see pink and blue versions in art by Jesús Alonso Iglesias and just the pink one in edited Joseph Feinsilver art and vis-dev art).
For various reasons, I prefer to just link to artists' own posts and portfolios. I also do not want to give additional credits (e.g. "art by x, based on the idea by y") because animation is such a collaborative effort, and crediting everyone who worked on a certain prop or location would take days!
There are some images that continuously come up when searching for concept art online. A lot of them are from this Animation Magazine article. If anyone knows who drew them, please do get in contact!
Christa Carr (visual development artist) designed props and environments.
Her design work for Mama Luna's Cat Sanctuary was also posted by the DreamWorks and Puss in Boots accounts.