I've had a few occasions of people creating a fake account with my photos.
Most of the replies above about watermarking don't really get to the issue you asked, so I thought I'd chime in.
Note that a fake account with my pics is different from adding my pics to their account. The former is rare, the latter more frequent. Let me explain. Some people snag their favorite pics of me and add them to their album of favorite IR pics. Most don't ask first, but some do. Since I post myself in IR encounters, I'm not especially bothered by a few pics showing up on other IR sites or guys albums. It's kinda flattering to be counted as their favorite.
Many guys have used one of my pics as their profile avatar, on tumblr and xhamster and other places. That's sexy as hell (hint!). But it's clear when you go to the profile that they aren't pretending they are me, or that they are the woman in the profile pic. Guys often use women as their avatar pic and I like that a real woman with curves is chosen instead of a tiny thin 20 year old (nothing against you 20 year olds, just some envy here
But when someone creates an account using my photo and is clearly a female or a couple, it implies it's me. Everything they say to others will be attributed to me. Every time they say they want to meet, they are misrepresenting me. Either the poor guy will show up and find a different woman, or perhaps only a man (weird), and be disappointed, or more likely they will show up and the fakers will have flaked entirely. I don't flake when I say I'll meet guys, it's rude and I don't want anyone doing it under the guise of my photo.
Luckily my fans are quick to alert me and my husband messages them. He merely asks they remove their profile or change the photos, no harm no foul. We don't blow a gasket. One reason not to is because my legit pics that I post are usually viewed far far more times than are those posted on the fake profiles, so it isn't like they disseminated my private pics far and wide.
Watermarking or face obscuring are the best ways to prevent your pics from being posted on sites you don't want them to appear on. That's a common and legitimate concern for most and was very much a concern of mine my first couple of years of letting hubby post my pics. But this post was about using your pics on a fake profile, presumably to misrepresent themselves as you.
Each time my husband contacted them, they immediately changed the pics or removed the profile. Because the stuff they wrote wasn't overtly bad, we didn't make a big issue of it. If they had written stuff we really would disavow, that would be different. But so far, all of the fakers are people who, I presume, are genuine fans of my activities and simply wish they had these experiences in their lives. Hope they can someday.
Note that both of the profiles below were not created by me. I wasn't visiting family in New Jersey (the C/L ad) and I don't live in Florida. The fetlife profile has "newly added" at the bottom, all pics of me, making it appear this was my profile. But they didn't use SecretPlayWife as their name so hubby created SecretPlayWife, and that is actually me (I'm not on it very often).
Sorry for the long post. I thought the subject warranted more discussion.