I would think that it is both a need for others to know, and a need to feel like it is a normal thing to be AB/DL. I felt the same way a lot in the past and then I stopped worrying about hiding things in my room. I think you start to develop an attitude where you might say, "this is my room, i deserve to be comfortable in it, so I don't want to feel like I have to hide in my own room."
That kind of a mentality is correct, but it is only safe in certain circumstances. Id say it probably isn't safe with parents, because you are better off letting them know in person, in my opinion, although you might not want them to know at all. It is also not safe if you live with somebody that might do something to ruin your life with the knowledge. When I moved out, I told my friend who I was moving in with about my little side and he was cool about it. However a bunch of the other guys I knew didn't know. I slowly got more and more bold in my room, stuffed animals everywhere, leaving bottles out, diapers not horribly well hidden. I eventually got cute wall stickers and a baby mobile. Some of the people I lived with asked me about it, others just observed and said nothing. I knew I was with people who wouldn't really do anything detrimental, so it was worth it to me to feel comfortable in my room.
Sometimes you have to live your dream and feel a little more like your room is actually a nursery. That is what I think that it is, at least that is what it was for me. I'd decide though if you really want your parents to find out this way. You may want to wait on exposure until you move out.