Thanks for sharing! I'm going to disagree with pretty much everything, so please stop reading here if you're not interested.
Imagine the person it is based off of finds out someone is doing that. That causes mental strain on the person...
Sure, and there are plenty of things that can cause mental strain, but that doesn't make those things illegal. For example:
public display of affection - could cause mental stain people who recently broke up or haven't found love
drug use - recovering addicts could experience mental strain
finding out someone is masturbating to a picture of you
And so on. Those things aren't illegal, but someone could experience mental strain from them. Experiencing that doesn't make you a victim, it just means you experience it.
revenge porn doesn't actively harm a person but causes mental strafe
Revenge porn damages someone's reputation, at the very least, which is a large part of why it's illegal.
Someone keeping those images for private use doesn't cause harm, therefore it shouldn't be illegal.
Someone doing something creepy for their own use should never be illegal.