"The term "image macro" was first coined in Something Awful[2] in 2004. In the forums, users could summon a number of default image macros using simple commands like [img – macro], for example, timelines, "Aces!" and "Captain Obvious to the Rescue!" images. The name is derived from the computer scientific definition of a macro: a rule or pattern that specifies how a certain input sequence should be mapped to an output sequence according to a defined procedure. The earliest definition of an image macro was submitted by SomethingAwful forum user Eclipse[3] on February 12th, 2004."

Hell, you could consider print advertising to be a form of image "macros". We need a better name that is descriptive or at least doesn't sound so abstract and far removed from the virality/humor aspect.