As it does every year, my local jinja — Shirahata Hachiman Daijin (白幡八幡大神) — has put a rice-straw and vegetable snake up on the inner torii.
This is part of a matsuri held on the first day of the rabbit in March, when an archery ritual is performed to predict the quality of the harvest for the coming year. The snake has a sword in its tail, which associates it with the snake/dragon killed by Susano’o in the myths in the Kojiki and Nihonshoki, but I do not believe that there is any close link to that story. The matsuri itself is associated with Inari Ōkami (who is enshrined in the jinja).
Snakes are, however, very generally associated with water in Japanese myth, including in the Susano’o myth, and water is very important for irrigation in rice agriculture. Thus, it seems most likely that the snake is symbolically about a request for a good supply of water for growing the rice, and other crops, without any flooding to destroy them.
The earliest surviving records of the matsuri itself are from the eighteenth century, but I do not know how far back the evidence for the snake goes. It is likely to date back before the Meiji period, in the late nineteenth century, because it is not part of the standard set of rituals established by State Shinto. While some jinja have created non-standard rituals since then, it was strongly discouraged in the pre-war period, and post-war creations have tended to be more closely linked to modern concerns. A straw snake with googly eyes looks like a surviving tradition. (Look at those eyes. Doesn’t it look like a surviving tradition to you?)
These sorts of matsuri often survive in towns and cities, because there are enough people living in the area to keep them alive. Even if few people still farm, they can still value local traditions.