If you look carefully, the word "Hello" is shaded in grey down this print. $25 for a decent sized poster (16in x 20in, or 41cm x 51cm), $9.95 for shipping (all prices $US) and does it have graphic impact? Heck yes! You can buy from MadebyGirl (and if you get together with a couple of TL pals, or you really want triple impact, postage for three posters is only a couple of dollars more than shipping one).
Image is from the MadebyGirl site.
Hello in lots of languages - educational too!
There are so many excellent online craft businesses, and plenty of poster ideas that aren't what you see everywhere and which compare favourably in price with the standard 'educational poster suppliers'. Take a tour through the search engine on Etsy http://www.etsy.com/, for example, and see what you can find to make your library special, exciting, a great place to be.
Framing can be expensive, but one option to consider is the single large piece of matte board with the poster laid on top, framed in a frame (like this one from Ikea, which is less than $10). Much better than either laminating or blu-tak. And, if you want to rotate posters through the same frame, you can.
I found the Hello poster via the design blog decor8. Here's another poster source from decor8: The Poster List. Certainly some ideas there worth thinking about for your school/library - modern, cool ideas and images. Or why not use this to challenge your vis. arts students to come up with images to display in the library?
PS. I haven't bought yet, because I'm not sure where I'd put it. But I am tempted - I do like this sort of use of typography, a bit bus-blind in style. Love vintage bus blinds!