Awesome animated graphic of the rise and fall of world empires from 1800 by Pedro M. Cruz. I did a double take when I saw this because it looked so much like the "found palettes" I'd been collecting from eBay. It's a category I think of as "graphic cousins" or "visual homonymns"--they have visual similarities, but little in common beyond that. If there is a word for this phenomenon, I'm not aware of it.
I tried to come up with possibilities for what the word might be, and started googling. "Homograph" is already taken and refers to words that have the same spelling, but whose meaning can only be known from the context in which it is used. "Homoglyph" is also taken. It refers to two characters or sets of characters that appear very similar and can often appear identical. Examples are the numeral zero and the letter "O", or the letters rn and m. "HOMO pict" has somethig to do with chemical bonding. "Homopict" has to do with another kind of bonding.
When I tried working with “icon”, Greek for "image", I found out that "Homicon", is an annual convention for fans of Homicide: Life on the Street, while "Homocon" is short for “homosexual conservative” an oxymoronic political identity. Google assumed there was a space missing in "homoicon", so I was taken to an art essay in the Independent, Arrows of desire: How did St Sebastian become an enduring, homo-erotic icon? “Sebastian's appeal to gay men seems obvious. He was young, male, apparently unmarried and martyred by the establishment." "Homoiconic", however, is a word used in computer coding. According to Wikipedia, "Homoiconicity is a property of some programming languages, in which the primary representation of programs is also a data structure in a primitive type of the language itself, from homo meaning the same and icon meaning representation."
Alas, being at a loss for one word, has caused me to use many.