Szajna produced paintings and prints, designed sets, directed theatrical productions, wrote the scripts to original shows and was a theoretician of the theatre. He was perceived primarily as a man of the theatre and creator of his own, personal formula, what Zbigniew Taranienko described as 'visually narrative theatre' (otherwise known as 'visual theatre', 'visual artists' theatre" or 'theatre of visions'). The emphasis in this type of theatre falls on visual expression. Unlike artists such as Leszek Mądzik, however, Szajna never rejected the actor, the actor's individual gestures or the spoken word. Nevertheless, the starring role in his theatre was undoubtedly awarded to visuals and imagery, often through expansive scenery and grotesquely over-sized props. Szajna himself was quoted as saying, "I transform life into images", a thought that accurately reflects his intentions. This innovative concept of visual theatre was realized most fully in his productions at the Teatr Studio (Studio Theatre), but it also defined most of Szajna's artistic experiences outside of the theatre. In his original morality plays (including Replika (Rejoinder) in 1973; Gulgutiera in 1973; Dante, based on The Divine Comedy, in 1974; and Cervantes in 1976), Szajna combined literary texts saturated with his own personal reflections with his trademark visionary organization of the stage and inventive, intense, expressive performances from his actors.
The artist began painting and producing prints during the 1950s, the same decade during which he began working in the theatre. These works demonstrated the artist's fascination with the Art Informel that was dominant in Poland at that time. Szajna initially produced collages, flat images made up of materials such as worn pieces of leather, chunks of rubber and fragments of fabric Obrazy-Dramaty (Image-Dramas). Then in the 1960s he began channelling his efforts towards assemblage, accenting textures in his compositions and adding in pieces of found objects (like mannequins, for example). The objects in these artworks – or rather pieces of them – were not treated as fetishes or "everyday votive items"; instead, they carried dramatic content and the traces of past traumatic experiences Postać V (Figure V) from 1962, and Dwoje (Two), circa 1966). As a result of Szajna's need to visualize his own experiences and to find an artistic medium that would best fulfil this need, he created entirely new spaces, an example of which is the environment-like project entitled Reminiscencje (Reminiscences) 1969.