I like Nautilus shells. They have the shape of a logarithmic spiral. This served me as a new inspiration for creating new pictures.
Note added on the 25th august 2017: The discussion in this post here was too obscure and is thus deleted to prevent headaches. You should look at the better discussion of https://geometricolor.wordpress.com/2017/08/25/spirals/.
The results depend strongly on the input image. I can get something resembling a petrified Nautilus:
or entirely different images: