The Chrono Cross concept art was completed by Nobuteru Yuuki, who chose a style more mature than his predecessor's, Akira Toriyama, to better suit the feel of the game. The art spread through player's guides and publications, though unlike Chrono Trigger's art, which had no official collection book, Yuuki's work appeared in the tome Missing Piece. It contained many sketches, including unused and beta versions of characters, location sketches, and other miscellany. Sadly, garish Japanese characters often appear over the official art, limiting one's ability to take the art from that book. Ultimania also features official art, unobscured by text boxes or writing; however, the art is slightly smaller in comparison to Missing Piece's.
Art is listed by character, then scene. Below these two sections appear scans of Missing Piece done by SilentMartyr; they allow a closer look at the official art and all the other interesting sketchwork in the book.
You can find location art on respective location entries in Locations (Chrono Cross), or you can download it all here:
Missing Piece Character Scans
Missing Piece Character Sketches
Missing Piece CG Shots
Missing Piece Location Sketches
Pre-Cross & Post-Cross
This gallery features a few pages from ANVIL III - The Man in the High Castle.