Visual tools help with memorizing words. Rosetta Stone and similar online versions like Busuu use it to train your vocabulary or short sentences. A word or sentence is shown with a picture added. Visualisation helps learning. However, just as learning a list of words without context restricts your vocabulary to a kind of foreign language grocery list, a picture of a ball or a color will not do too much for your vocabulary training. A picture should tell a story.
Art and Language Learning
The art in the Fairytales and Short Stories products has been selected to fit into the story. Actual paintings of Fairytale or everyday situations tell a story by themselves. And they help your memory to attach its new-found knowledge somewhere. A picture that tells a story stimulates the brain. However, it should not be overrated.
The Visualisation of The Story
Even though the added art is beautiful, the most visualisation actually occurs just by reading the story, even without pictures. This visualisation is simply the brain translating the words (unnatural) into pictures (the natural form of everything around us as seen from your eyes). It is this visualisation that is helping you memorize the individual parts of the story, its sentences and words, into a natural language scheme. As opposed to old-school word list cramming or even learning words like German gelb (yellow) or Obst (fruit) having a picture of a banana to go with it. By the way, even as you read that last sentence, you will have pictured a yellow banana already :-) So much for the need of pictures. Your brain will do the job. But as we began this paragraph, the added art is beautiful in itself.