Google is now displaying image thumbnails in the main web search results page when you do food-related searches. It seems most searchers are seeing this now, something Google has tested one way another for months.
I do not think it is related to the new rich cards feature that is available for recipes and movies. It seems that this works on non-recipe websites as well, without the structured markup.
Here are pictures of how it looks for various food-related queries on both desktop and mobile Google results: