It’s far too late, but would not the best way be to write to the currency issuers and ask for specimen banknotes? Real banknotes, but with an obviously fake serial number and SPECIMEN printed on them. Note that you’ll have to find those countries which distribute them widely.
That’s what I was going to recommend. Most exchange bureaus don’t take change, so after every trip, I’ve ended up with a pocketful of change that I couldn’t convert, and I’d have been happy to donate it to a school project coming out of the airport.
For larger denominations, I know my bank (Wells Fargo) can exchange it for you, but you have to give them a certain amount of lead time, and probably a minimum amount to exchange as well.
The countries embassy/consulate would be a good place to look.
I doubt it, not all countries embassies are the fortresses US embassies are but none are going to want to bother with that kind of request.
They usually are more than happy to give you information on the country. They might not have notes handy, but they may have samples or pictures.
here the english version of the UNICEF site as translation - EUromoney24 has an english site anyway.
http://translate.google.com/translate?sl=de&tl=en&js=n&prev=_t&hl=de&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.unicef.at%2Funternehmen.html&act=url&act=url&act=url
Sounds like a new poster is trying to drum up UNICEF donations.
I third the ebay advice. I have a nice collection of weird currency from there.