The Elections ephemera at the LSE Library covers general elections dating back to 1945, although there is some earlier material. The material is catalogued but not digitised.
Other online resources with digital images include Posters (Political and Tariff Reform Posters, c1892-1910; British Labour Delegation to Russia, 1920; Russian Child Care posters, 1930; London County Council Election 1907) and Online exhibitions, e.g. CND, the story of a peace movement and Turning points: three key elections of the 20th century (1906, 1945, 1979).
|Poster: (C) London School of Economics|