This also applies to the ICA postcards in my collection. They were published by the German camera manufacturer ICA in the 1920s and were intended as promotional cards. After ICA merged with other camera manufacturers into the Zeiss Ikon company, the postcards remained in use and were branded Zeiss Ikon.
The postcards are a series of beautiful coloured cards of people with their camera. There were German and English versions of the postcards. Some of the images were also used by ICA on the covers of their catalogs. The postcards were designed by the Austrian illustrator Theo Matejko (1893-1946). He was a well-known artist and involved in the design work for the posters of the 1936 Olympic Games in Berlin. The cards contain his signature and the year 1925.


It was not uncommon for camera manufacturers to use renowned artists to design their promotional material. An important competitor of ICA was Ernemann and that company contracted the Art Nouveau painter Hans Unger to design the Lichtgöttin (goddess of light) which was the famous Ernemann logo until 1920.


The last postcard is doubtful. The style is a bit different and the signature is difficult to read. It's probably designed by another illustrator:

References:
- Theo Matejko on Wikipedia
- Zeiss and Photography, Lawrence J. Gubas, 2015