This site has some great suggestions for making beautiful posters. It talks about white space, font, color etc. It has links to hundreds of great examples to look at.
"Poems for... supplies small poem-posters for public display - in class rooms, libraries, waiting rooms ..." You need to register before you can download, but it's free -- and the poems make lovely A3 posters printed out
Academia has lots and lots and lots of systems in place for assuring that credit is always given where credit is due. If you're writing a paper, there are particular ways to cite internet sources-- even tweets and Facebook posts.
But what about on the internet? We know we're supposed to cite sources, but a standardized system hasn't developed, and in the meantime, you could face a lawsuit if you steal someone else's work, even by accident.
Does that mean you can't ever elaborate on someone else's ideas or repeat a little of what someone else said? Of course not. Just use some common sense and always err on the side of caution.