Like the hands, the foot is usually a very sensitive area, therefore, delicate to perform a tattoo, you should analyze how wide your pain threshold is, since some people resist more than others. The tattoos on the feet are preferably small and can be any reason you want, for example:

Eclipse: They are the duality of the sun and the moon, the conjunction of two energies. Love and understanding Moments of light and darkness.
Birds: Although the feet are on the ground, it does not mean that you can not fly. You can carry a bird on the foot that you like the most.