I want to keep nudes that girls send me
Why do you want to keep nudes?
They make nice memories of the times my friends and I where hanging out
If these women gave those photos to you as gifts, then that was their decision.  However, you should be aware that someone else may come across the photos and recognize the person in them. Instead, you should keep the memories of such things in your mind, or at least, in a secure location.
I'm going to ignore a lot of what you are saying because I know what I like.
I understand that you have your preferences, but don't you want you and your friends to be safe? Holding onto these nudes can be dangerous, so at least don't store them on devices that you carry around with you.