Adult movie posters, via we make money not art, who got it from Camp Heatwole.
edit: more linkworthiness. Dazzle painting, via gravestmor. It’s worth looking at the pictures and clicking on the links in the dazzle article.
further edit: Bangladeshi rickshaw art, via Metafilter.
and still more: Crop Art, also via Camp Heatwole.