As from 1913, however, Seewald worked with Hugo Ball for the Münchner Kammerspiele (Munich Chamber Theatre), where he designed stage sets and costumes. In Ascona during the 1930s, he wrote theatre pieces for marionettes for which he also designed the settings.

Seewald was invited to design his first stained glass windows by Richard Riemerschmid, who in 1922 was president of the art committee of the Deutsche Gewerbeschau München (German exhibition of the applied arts in Munich). He was commissioned to produce four stained-glass windows for a chapel. Later he was asked by the Arts Institute of Detroit to paint the Four Seasons on glass, and to produce a triptych in the old people's home in Rüstringen (today Wilhelmshaven). The latter was destroyed in 1934 due to Seewald's inclusion on the list of "degenerate" artists the year before.

1928, he executed a large painting for the opening of Cologne airport. Commissioned by the city's Lord Mayor, Konrad Adenauer, the work was later donated by the City of Cologne to the German Museum in Munich. During the same year Seewald painted the mural Views of Lake Maggiore in Cologne for the garden pavilion of the museum director, Dr. Julian Schloss.

In 1931 the architect Dominikus Böhm asked Richard Seewald to paint murals in Stella Maris Church on the island of Norderney. Various commissions followed in Switzerland and Germany to create stained glass windows, frescoes and tapestries for sacred buildings. In 1932 Seewald made designs for tapestries to be hung in the Reemtsma residence in Hamburg, which were executed by the Gobelins manufactory in Munich. Today they are conserved in Altonaer Museum in Hamburg. The wall carpet Masken und Mimen (Masks and Mimes) was created in 1953 (handwoven at the company Geiger-Wörner in Ligerz). For the execution of the tapestry Zirkus (Circus), Seewald approached a weaver in Ronco. In 1936 he painted the altarpiece for the Chapel of the Holy Annunciation in Ronco, which was destroyed by a landslide in 1943. In 1967 he decorated the Capèla del Nusétt in Ronco with a fresco dedicated to the memory of his wife Uli, who had died the same year.

During the 1940s and early '50s Richard Seewald produced frescoes and stained glass windows for the churches of Maria-Lourdes and St Teresa (Theresienkirche) in Zurich, the Guthirtkirche (Church of the Good Shepherd) in Aarburg, the Church of St Borromeus in Magadino, Regina Pacis parish church in Wiler, the cemetery chapel in Dötlingen, St Adolf's in Düsseldorf, and the Herz-Jesu-Kirche (Church of the Sacred Heart) in Munich. Characteristics of these works were their bright and highly contrasting colours, and their great expressive power.

The mural decorations for the Banqueting Room in the Gürzenich Palace in Cologne date from 1955 but their scenes featuring plants and animals were executed in delicate colours. Richard Seewald invested his wall paintings with a refined sense of composition, for which he took into consideration the architecture and the spaces and their use.

In 1961 he painted the frescoes on the arcades of the Hofgarten in Munich, inspired by sketches he had made during trips to Greece and the work Glanz des Mittelmeers (Splendour of the Mediterranean). Seewald executed his last wall painting in 1976, the Story of the Genesis, for the parish hall in the Herz-Jesu-Kirche in Munich.