[MostAwesomeDude]

Image macros come from Japanese message boards; they are not really related to the faux motivational posters that are commonly known as "demotivationals".

[astrange]

Image macros came from SomethingAwful, although even then it was only a brief period where they were actual "macros".

Japanese sites don't even let you embed images. Everyone uses ASCII art (actually SJIS of course).