I make very non-traditional altars. As a San Francisco apartment-dweller, they have to be crammed in with everything else. In my last apartment, my multi-level plant stand became the main altar, with each of the five shelves being the various elements from bottom to top (earth, water, fire, air, spirit).
Here's how the air shelf looked,
In my present apartment, the corner shelf part of my bookcase has taken on some altar duties, only now I have more shelves. From bottom to top they are earth, water, fire, air, ancestors, spirit. Those are fairly set, and the top of my entertainment center is the "active" altar, where I keep fresh flowers, larger items and do seasonal arrangements or special groupings depending on my spiritual work.
I should try and get some pics of those up for you to see. But I feel the need to dust first... LOL....