As for replacements, Intellect Devourers fill the "evil psionic-like overlords" niche, while I'd take Decapus as the beholder stand-in.
Since there are no official psionic rules I don't use these much, but really good choice. I picked the Ogre Mage because it has the intimidation factor that mind-flayers also possess. They just both seem more imposing.
You are correct about the dragons,and I apparently was not clear that this is all just my opinion. It is completely subjective and I was not attempting to portray it as fact. It is just an image association/perception that I have noticed, based solely on my own personal observation, on various blogs and message-boards. I've noticed a lot of people making an association between black dragons and Pathfinder. While the blacks have only appeared on two covers that I know of, I've seen people comment about their apparent more numerous interior appearances. I can not confirm this as I do not own every Pathfinder product, so I took their word for it.
I also must apologize for not making my question and the spirit with which it was asked clear. So I officially withdraw it. If a mod could delete my posts on this thread I would appreciate it.