The flag of Afghanistan between 1880 and 1901. The file is a solid black rectangle, and we also use it for the "black banner" of early Islam, i.e. the "Abbasid flag", i.e. the black flag used in the Abbasid Revolution from 747; equivalent in appearance but with a more intuitive (albeit misspelled) filename, File:Abbassid banner.svg may be used for that..
Own work
PaD and Indolences.