Paintings by 54 artists, using materials ranging from Plasticine to industrial aluminium foil, have been selected by a panel of four experts.
The act of painting itself is a theme explored within several works, which will be showcased at Liverpool's Walker Art Gallery from 9 July to 27 November.
A shortlist of four artists will be announced in June, with the overall winner unveiled on 7 July.
The sources of inspiration behind the paintings are varied, ranging from George Orwell's Animal Farm to a statue of an assassinated politician.
Director of Art Galleries at National Museums Liverpool, Sandra Penketh, said there is an "especially vibrant use of colour" in this year's selection.
"We also see many artists addressing the topical issues facing our world today, touching on subjects such as migration."
The entries were whittled down from more than 2,500 pieces by jury members Gillian Carnegie, Ansel Krut, Phoebe Unwin and Ding Yi, and author and freelance curator The Reverend Dr Richard Henry Davey.
Previous recipients of the prize include David Hockney and, most recently in 2014, Rose Wylie from Kent.
Sir John Moores, the owner of the Littlewoods company and a keen amateur painter, founded the competition to challenge London's domination of the national arts scene.
It was first held in 1957 and is open to anyone.
The longlist for the John Moores Painting Prize has been announced.