Posters were already a major vehicle for political propaganda, commercial advertising and promotion in the 1930s when the Shamir Brothers started their commercial art activity in Israel. A year after they immigrated to Israel they designed their first public poster – for the 1936 Levant Fair (Yarid Hamizrach). In those years they designed posters of products for numerous local manufacturers as well as the newspaper advertisements for these products. At the start of local mobilisation to the British Armed Forces during the second world war the Shamir Brothers designed posters for the Jewish Agency, recruitment to the Women's Auxiliary Air Force (WAAF), the Auxiliary Territorial Service for Women (ATS) and the British Navy. Many of the posters appear in History books covering that period. With the establishment of the State of Israel the number and range of clients for posters designed by the Shamir Brothers grew significantly: Government Ministries, Municipal Authorities, public bodies such as the Israeli Labour Federation (Histadrut) and the Jewish Agency (KKL), commercial companies such as Assis and Bejerano Cigarettes and various political parties including the Workers of Palestine Party (which became the Workers of Israel Party - Mapai), the Revisionist Zionist Party (Herut) and even the Zionist Religious Party (Hapoel Hamisrachi).

In the early days the posters were designed and drawn by hand including any depicted people and products. The use of photographs within the design only started at the end of the 1950s. Fonts used in the posters were created by the Shamir Brothers uniquely for each of the posters and were designed to reflect the message conveyed. Their design of a poster was often aligned with their designs for the accompanying newspaper ads, product packaging and even the transparent (positive) cinema slides.

Gavriel Shamir left in his estate 110 posters. His sons placed them with the Central Zionist Archives who already had 50 other posters by the Shamir Brothers in their collection. Since 2004 additional posters by the Shamir Brothers were discovered at the Lavon Institute, the Jabotinsky Institute, Israeli Defence Forces (Zahal) Archive, the National Library, at various auction houses around the world and in private collections in Israel and abroad.

Posters have become collectors' items in recent years for serious collectors as well as younger interested parties. Some of the trade in posters has been found to verge on illegal trading where sellers print unauthorised reproductions of sought after posters violating the Intellectual Property rights that will belong to the heirs of the Shamir Brothers till 2060. Exhibition curators, researchers and writers who ask in advance for approval to use or display works by the Shamir Brothers will usually and gladly be given the requested approval.

It is clear from old photographs, newspaper clips, old documents from the Shamir Studio and International Graphic Art magazines that some of the posters designed by the Shamir Brothers have yet to be discovered. Some of the missing posters could well be in large collections such as the Judaica Collection at Harvard (where the items are not sorted by Artist names) or in the collection of the Tel Aviv Municipality (which still sits in boxes in Ashdod). In addition, an entire family of posters that were printed in colour on metal tin-plate is still to be unearthed.