Not sure if you can change it in the title, but you can add it next to the link when you post it.
Putting the NSFW warning there is a nice courtesy that helps one stay out of trouble with employers who monitor web usage. I go to many pro photogs sites that don't have material I need to worry about at work, it's nice to know in advance that I need to look at the site when I get home. It's not so bad when fine art nudes are in a seperate album or take another click to get to the art on their site, but when it comes up on the opening page it can be troublesome.