Technically, the bill board should read 'Organa-Solo', not 'Organa'. Now get your ass in here so I can pos-rep your AV
How do you know she took his name, that they would be the sort of couple to do that hyphenated bullshit, or that they got married at all? Maybe she wanted to go help restore democracy on Coruscant, and he wanted to keep buzzing around with Chewie in the Falcon? Then again, maybe Luke went back to help rebuild the ruins of the Jedi temple, and so the only other place with friends for Han to visit was the Cloud City. Shit, poor Han. Probably went out fat and drunk, embarassing his wife at social functions and reminiscing with a greyed-out old Wookie about the good old days.
Han and Leia did get married and she does use the hyphenated name (I think). The question actually is, was this billboard put up before or after her marriage?