When looking at swirling vapors, forms and figures seem to appear and disappear from moment to moment. Similar to seeing faces in clouds, rocks or tree bark, this psychological phenomenon is known as Pareidolia.
For any particular image or natural pattern, not everyone sees or identifies the same form, if any form at all. The strength of the effect varies, too, so a form may be clearly identifiable or merely suggested.
Here’s an example from my collection of vaporous macros, in which I see the vague outline of a matronly figure: