It seems unlikely that there are any other unofficial words when you consider George has created over 400 Houses. On top of that he hasn't even made up all the words for those ones. There are some big houses like House Frey that don't have words yet too.
Could you tell us some of the family words for those families we haven't seen yet, for example the words of House Frey?
I'd have to see whether I've created those words, I can't remember off-hand. I've a mountain of notecards at my home where I put down all this information. You have to realize I've made up more than 400 houses, and I haven't created words for all o them yet. I make them when I need them. Where's Elio when I need him?
So Spake Martin, ASSHAI.COM INTERVIEW IN BARCELONA
With that said George has suggested using "Sapphires" as a replacement for the words for House Tarth at a book signing as he hadn't come up with the words yet.
When it was my husband's turn to get our books signed, he told him he wanted the Stark words in two books, and the Tarth words (whatever they were) in the third. George said that he hadn't ever come up with words for the Tarths (maybe he will, now!) He laughed and said if we really wanted something about Tarth, he could just write "sapphires" - naturally, my hubby said, "no, sapphireth!" But ultimately he just put "Winter is Coming" in all of them.
So Spake Martin, US SIGNING TOUR (ALBUQUERQUE, NM)
This is only really an out of universe replacement rather than in universe unofficial words. However, sapphires are used by Jaime to keep him and Brienne safe by Vargo Hoat's men even though Tarth isn't called the Sapphire Isle for gemstones.
"Is every word you say a lie, Kingslayer? Tarth is called the Sapphire Isle for the blue of its waters."
A Storm of Swords, Jaime III
Of course this goes on to help them be saved from numerous unpleasant dates whilst in the encampment. The following passage also goes someway to describe the reference from the person's husband at the signing.
Cursing, Rorge kicked at his stump again. Jaime howled. I never knew there was such agony in the world, was the last thing he remembered thinking. It was hard to say how long he was gone, but when the pain spit him out, Urswyck was there, and Vargo Hoat himself. "Thee'th not to be touched," the goat screamed, spraying spittle all over Zollo. "Thee hath to be a maid, you foolth! Thee'th worth a bag of thapphireth!" And from then on, every night Hoat put guards on them, to protect them from his own.
A Storm of Swords, Jaime IV