I'm going to set a profile picture of a random tattooed girl on my whatsapp
Why would you set a picture of another random girl on WhatsApp?
The girl has a nice tattoo that I think is very pretty.
People are going to think you are her. That is being dishonest and a bit creepy as well.
I don't care. I just want to have a nice picture as my profile picture.
What if the person in the picture uses a photo search and discovers what you did? It's wrong to appropriate someone's photo without permission, and misleading to your followers.