I used the following mystery picture with pre-intermediate students towards the middle of the course. We had been talking about homes and about country and city life, so I thought it would be a good way to see what they remembered in terms of vocabulary.
When I asked “What are you going to see in this picture” and all they could see was the only uncovered area in the initial slide, the vocabulary items produced were: a square, more houses, shops, a harbour, a hospital. Here, “harbour” was a new word that only one student knew, so the other students benefitted from this.
After removing the first rectangle, they said that they might see “a park” and “cars”. I removed a rectangle and asked them about some final predictions before uncovering the rest. Their bets were: “bus”, “fountain” and “supermarket”. Again, “fountain” was a word which most of the class didn’t know.
The description of the complete picture included all the vocabulary elements expectable from this level, with no major difficulties.
My conclusion is that this mystery picture is productive in terms of eliciting words from the semantic field “city or country life”, because most of the words that came up while guessing belong to this semantic fields and helped students revise the vocabulary they knew and learn two more words thanks to their contributions.