Thank you so much!! In the process of planning a campaign myself with it currently, so best of luck to your own endeavours!!
As for art - the interior art is all taken from in-game assets with the exception of the Super Mutant and Ghoul art for the mutant medical history; I couldn't find a perk icon that used a ghoul or super mutant in that classic style so I busted out the ol' image editing software and made them myself, with designs largely inspired by how they are seen in some fallout 76 UI elements. The cover is an edit of some existing resources. Finally, the character sheet is all me!
As for the Mutant Menagerie; its gonna try and cover all the big, wasteland wide, creatures and enemies one might face. It wont have more unique/specific things like the spore carriers, mothmen, or wanamingos... at least, that isn't the current plan! At the very least it should provide enough examples that folk brewing up their own mutants and monsters shouldn't be too hard to do!