Yes we'd love to have seasons. As you say it would required lot of new art, but I think we'll do it anyway, just don't know when. Also we'd had to redefine when the plants grow and make fruit, and it would make a lot more sense.
Animal reproduction would also occur at a certain time of the year, as well as some disasters (for example lightning storms are more frequent in summer).
Winter would be a hard period with less food to gather and firewood to consume to stay warm.