-Stamp # 1 utilizes organic-like lines and curves that are the hallmark of the classic art nouveau style.

-Stamp #2 is done in 'pop art' style, which falls into the 'post-modern' category. It uses bright colors and focuses on object contours to build visual tension. 

-Stamp #3 is an example of the bauhaus art movment. The constructive use of blocks and shapes, combined with the typography are traditional characteristics of the bauhaus style.