I'm really looking for a subtle way to proclaim our geekiness through a shower curtain. As far as geeky shower curtains go, I began with ThinkGeek, who normally meets most of our geek needs. Sadly, their selection wasn't as expansive as I would like, but they do offer the classics such as the periodic table curtain and the horror movie shower curtain.
They do also support two new shower curtains that I haven't seen everywhere else. One of the curtains pays homage to puzzle game by Valve Corporation, Portal 2. It's a simple shower curtain that sports the Aperture Laboratories logo.
The last shower curtain is decorated with an anatomically correct skeleton that is correctly labelled.
Leaving the domain of ThinkGeek and traveling through the rest of the interwebs will dig up more geek worthy bathroom decorations.
CafePress tends to be gold mine with properly themed decorations, a quick search of Star Trek, circuits, or Area 51 will bring up plenty of shower curtains that your Aunt Meredith is sure to not have.
Etsy is another online community that caters to those with nerd tendencies. Eternalart has an impressive binary shower curtain that is hand painted up for sale.
But my absolute favorite shower curtain that I've found is this Doctor Who themed one that Autogeography has for sale. It will most likely be hanging in my bathroom in the near future.