Keeping altars is probably one of the most consistent things we do as Pagans in our personal practice; though "altars" (and if you insist on using this word, please spell it with an "A"; "alters" is a process of forcing change) would not technically be the correct word. What we keep are actually "shrines," places where we make images of the Divine and our spiritual practice, worship and make offering.
I keep an awful lot of altars myself. My household altar is now located in the centerpiece of my living room, which is a beautiful mirrored china cabinet gifted to me by my mother-in-law. It contains my ritual tools, statues of the Deities appropriate to the time of year, antlers to honour the Horned God, pine cones to honour the Earth Goddess. The image you see at the top of the page is the central top shelf of my household altar, which currently is adorned with the pentacle of my tradition (which I'm pretty proud of; it's solid copper and was handmade by one of our founders, Mistress Leia,) an image of Osiris (to symbolize the God who was dead and is now reborn,) and the Star Goddess (which was a white clay figurine I purchased and then painted.) In the center you'll find my personal pentacle (handmade by me,) a terra cotta incense burner with a turtle (placed there for feng shui value and also for a Terry Pratchett reference,) my Moon Crown (purchased several years ago from Lobelia's Lair in Nanaimo) and behind these, underneath the tradition's pentacle, my wand (also handmade with a lot of personal symbolism I don't care to publicly share at this time.)
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I think you and I (and probably myriad other pagans too) are on the same page when it comes to altars - Lovely piece. http://witc