Tomi Ungererparadoxically made a living producing political posters, children's books and visual erotica. Again clarity of message, simplicity of palette, visual balance between light and shade, positive and negative.
Poster produced by the radical Marxist revolutionaries Atelier Populaire [see more here]during the uprising in 1968. Simplicity/Clarity/Immediacy. At the time the production of these posters had to be quick and immediate, with posters being ripped down almost as soon as they were put up. Ideas and opinion were communicated directly and in a partisan manner. Probably some of the best examples of the poster as communicator/influencer/manipulator.
A series of poster images by the Japanese master Tadanori Yokoo. These are complex and involved images involving disparate visual components [perhaps think about how you use your kit?] which are unified through a clever use of colour and process.
Some imagery here courtesy of the Non Format website the design company responsible for the original [and best] design of Varoom magazine. Take note of the image/typography overlap, the letter forms 'just' retain their legibility but start to assume the more poetic potential of abstract imagery. It is a fine line that is being tread but can give the Illustrator scope to include typography that is both expressive [meaning it can carry forward an idea beyond the literal] and communicative.
2 poster images by the great Eduardo Munoz Bachs, Cuban poster artists/designer working consistently for the ICAIC[Instituto Cubano de Arte e Industria Cinematográficos] over the 60's and 70's. Often using 'vernacular' hand rendered typography to complement the idiosyncratic imagery. Look at the simplicity/clarity in thinking regarding color and composition and the use of 'edge' as well as line to distinguish between one form and another.