there's not a lot of them but the few full color concept art images from 1st gen AC really are crucial if you wanna understand the actual extent of the detail and effort they put into these designs that inevitably couldn't be fully realized due to the PS1's graphical limitations
Where were you in 1984 when Namco's robot band, Pic Pac, was shredding it up? They actually make a reappearance virtually in Namco Museum Vol. 4 on PS1. Neat.