That's what I thought when she said poster. But by poster she just meant a semi-artistic representation of what people on the left and right generally believe in.

Why didn't your teacher just call it a diagram?

Because A) that sounds more boring and B) I'm not an artistic person, so I'm thinking she is expecting it to be a bit more poster-esque. I can guarantee I have put the most effort in out of everybody, though, so it's okay.