I keep a decorated broom (besom, whatever you prefer) above the doors in my house. Each one is coordinated with the rooms theme. I also have a cute little country witch on my front door that my mother in law got me. Its says "Welcome my pretties".
You could go with themed rooms and use the elements as inspiration, like:
Kitchen : Air (all the great smells that arise...)
Living Room: Earth (the center or core of the home)
Bathroom: Water (obvious reasons)
Bedroom: Fire (well, you know ::wink:: ::wink:
You could have a cluster of shelves on a wall, making on a subtle altar that non-pagans wouldn't really notice, but means something to you.
I can't really think of anything else right now. But you've got my brain working. Thanx for posting this, I'm curious to see what others say as well.
Good luck, blessed be