As I think I have mentioned, there is no such thing as too many gods. However, there might (might!) be such a thing as too many altars. Personally, when it comes to altars, my philosophy is “the more the merrier.”
Others in my household might disagree. My partner, for example, does not want an altar on his chest of drawers–he wants to be able to put spare change on it, or his hairbrush. Meanwhile I am starting to eye the flat shelves that are balanced on the radiators…
This is not uniquely a multifaith issue. Plenty of pagans are fond of altar-building. Plenty of us have many gods and perhaps many altars. But it’s probably true that being multifaith means more gods, and more gods means more altars, or at least the desire for more altars.
I’ve actually been giving more thought to options for wall altars, wall shrines. Years ago I decorated a wooden shelf for a Dionysos shrine, but since all my wall space was (and still is) in high-traffic areas it didn’t work very well. Things got knocked off. It wasn’t good.
I’ve considered the possibility of making a shrine from a medicine cabinet, the kind you hang over the sink in the bathroom. They come in different sizes and although they are generally shallow, there’s enough room for images inside, or even small icons, and of course they are designed to hang on walls. I haven’t tried this yet but I think there are possibilities there.
I think it depends on how the space will be used. If you are going to leave physical offerings you need a place to put them. If you simply want a place to pray at, an appropriate picture or plaque on the wall is probably enough.
What I’ve got right now is this:
I have three altars that occupy the tops of chests of drawers.
I have two altars that occupy the tops of bookcases.
One shrine is in a cabinet purchased for the specific purpose of being a shrine.
Another is in a cabinet on the left side of a buffet I use to store clothing; I’ve decorated the “walls” appropriately and have attached fairy lights to the “ceiling” as a light source.
I have two shrines that are pretty much just on the wall and one that’s art right now but is going to be a more active shrine soon.
I am undecided as to whether the Hermes beads hanging from the rear view mirror in the car count as a shrine but I do talk at them on occasion.