[hELLO wORLD]

Okay, the petition model is good.

I think we can bring artworks like images or movies or what we want. If someone is excelling in something like image design and it is a passion for him, he can bring his work. however, the result (= the acknoledgment letter) must be a big unified thing and not multiple little works...
I think of one printed letter with a beautiful picture, an acknoledgment sentence, and our signature (printed, not real, of course...)
If someone works in a print shop, he can help by printing this letter.
If someone want to do a really cool and adequat picture, he can draw it, with the suggestion of anyone that is interested on this project.
A real letter will have more impact, in my opinion, but it is only an idea. It depends also on the number of participants... I mean 4 signatures will be ridiculous.

I like the way Apple says "Thanks for your help and for being a part of Apple history. We couldn't do it without you." in the Public Beta Package. I think a sentence hewd in the same wood could be great.

I am not good in English, and I think the first thing is to find this sentence...

Maybe something like :
"We are proud to being part of Apple history, and we want to congratulate and thank this thinking different company and all its employees that brings us an Operating System that is being made and conceived for us.
Thank you for your time, your patience, and your difference !

Long life to Apple !"