Mostly through Chrono'99 and Darkken, the Crimson Echoes team developed several new sprites for use in the game. You can find most of them in the Beta Stuff page. Ones that appear in FaustWolf's video series, recorded towards the end of the development, are considered "finished" and presented here.
The Dragon Tooth artifact, instrumental in King Zeal's creation of the Reptite timeline, and used in Chronopolis's reactor after recovery.
The Frozen Flame, and a "crimson echo" in its own right.
Kasmir, leader of the Mystics in the timeline without the Masamune.
THE MAN himself, King Zeal!
King Zeal's final forms. The middle image is his idle stance, and the opened Lavos eye represents spell-casting.
Ayla's child, Noah.
The Epoch II, converted to a single-seater "Neo Epoch" in Chrono Cross. Chrono'99 did an awesome job with this one; the designs completely match.
Lebniz, the boss of Singing Mountain.
The Dragon God, boss of the Lucca and Robo chapter.
95%-complete human Glenn sprite-sheet.
Darkken's finished piece for Glenn.