Walter learned drawing and painting from his father, Walter Peter Koller, a renowned Guatemalan painter. Peter’s education includes studies in Philosophy and Architecture at Francisco Marroquín University in Guatemala, as well as courses in drawing, ceramics, and sculpture at the School of Fine Arts in Zürich, Switzerland, and Visual Arts at the Superior School of Art PLART at USAC, Guatemala. He has also served as General Director and Professor at his own art school, ARS ARTIS, since 1993, and as a Professor of artistic drawing at the Faculties of Architecture, Interior Design, and Graphic Design at both Istmo and Rafael Landívar Universities.

Walter won First Place at the Art Competition of the COG, allowing him to participate in ART & SPORT 2000 of the COI in Lausanne, Switzerland, with Purpose, the Archer, which expresses how man must aim at himself in order to succeed in life—this life, his life.

The sculptor has immortalized a significant number of illustrious Guatemalan and international figures through various busts and full-body sculptures, including Isabel Gutiérrez de Bosch, Yolanda Toledo de Leal, Luis Schlessinger Carrera, Ricardo Castillo Sinibaldi (Cayo), José Luis Gabriel, Juan Bautista Gutiérrez, Juan Mini Feltrín, Mario Gabriel Ruano Batres, Gustavo Argüello, Alejandro von Humboldt, and others.
In May 2014, his chiseled beige Guatemalan marble masterpiece, Dawn: The Giant of Cayalá, was inaugurated at Paseo Cayalá. It is the largest sculpture in Guatemala, measuring 55 feet long and 9 feet high, a piece that took him more than three years to complete and expresses "The Pursuit of Happiness."
In September 2016, his 13-foot-high monument, The Muse of Innovation, was inaugurated in front of Tower 2 at the Campus TEC. His most recent monument, The Connectivity Force, was inaugurated in September 2017 at the corner of Tower 1 of Campus Tec at 4 Grados Norte. In 2019, The Inventor, a 3.75-meter-high sculpture, was unveiled on the corner of Tower 3 of the same TEC.