In my research I found posters for War Bonds during both World Wars particularly interesting. I think these posters would have a lot of relevance to LinkedIn because of its image of a social network for professionals, with many employment opportunities existing. For this idea I was thinking along the lines of a slogan that plays on the idea of 'Investing' your time in LinkedIn for some financial/career gain.
The above image is a poster created in 1917 encouraging the purchase of 'Liberty Bonds' to help finance the US involvement in WWI. I really like the very simple colour scheme of this poster because it gives it a very distinctive aesthetic.
I also find the image below very interesting because it has a very similar palette to the first one, despite being of a much later era. Its design is much more simplistic which I find gives it a very striking look.
