We could read churches.
I have always loved the ideas that churches and cathedrals in particular are the Bible written for illiterate people. That stained glass and sculptures tell the story of God from early days to Kingdom come. I spent 4 years studying how to teach reading to little children and one of the first things we learned (thanks to Marie Clay having a prominence in pedagogy then that she seems to have lost now) was that every child can read, but just not words.
The example oft quoted back then (and more true today) was that a 3 year old would recognise the Golden Arches as the symbol for McDonalds and that reading is really just advanced symbol deciphering.
I wonder how complete illiteracy would affect me. Would I seek to make sense of the things and pictures around me? Would I stand and look at the windows and wonder who all the people were? Would familiar stories jump out at me and say, 'here is Noah, here is Abraham, look, see Jesus being baptised'.
Would I be irritated if someone were more visually acute than me, who knew what all the stories were.
Or would I be too busy picking a slim living from a few strips of land to care what was before me? Is literacy a treasure only available to the well fed? And has so much changed in 1000 years?