i love everything ralph mcquarrie has done. for those who don't know, he did most of the star wars concept art, but he's also done his own pieces too. i have seen unreliable sources claim that this is an early bespin or coruscant concept, but take that with a pinch of salt
higher quality image, but cropped (and with the signature removed):
main image source || hq image source || ralph mcquarrie on wikipedia
Ya they were never super important but they popped up In a few of the books and comics. I think a crime lord named Prince Xizor had one that was like a luxury mansion