One sees something like that and the picture forms in one's / their / his / her mind?
Which of the above possessive pronouns are preferable/correct?
The posessive pronoun you're looking for is referring to the subject, "one" in your case. In this situation the correct usage is "one's":
One sees something like that and the picture forms in one's mind.
When the subject changes, you will have to change the posessive pronoun:
Mike sees something like that and the picture forms in his mind.
People see something like that and the picture forms in their mind.