Relax! There are no altar police. You can put whatever you want on an altar. Most traditions have some guidelines but there is no one true way. No matter what anybody else says. If you want you can make your whole house an altar. You can put one in your car. You can put one on a wall or you could hide one in plain sight on your desk at work.
The minimum usually is 4 corner candles, a deity candle and objects to represent the 4 directions. But you don’t even have to do that if you don’t want to, period.
I have an altar in my bedroom for private ceremonies and we have a family altar in the living room. Most people seeing this altar don’t even realize it is our working altar. It looks more like a weird collection of toys. Why? It consists of a fountain that looks like a big rock, several toys from the Playmobil Magic set ( a goddess, a faery, a druid, a witch and 2 Green men). It also has a interactive Yoda (wise teacher), a talking Buzz Lightyear, (guardian), several faery figurines and a talking Ent (another Green man). It has a statue of Sekmet and Kwan Yin. A large statue of a woodland Goddess/tree. It also has several glass votive candles. It also has a bottle of water from Brighid’s well in Kildare. It covers all of my family’s interests and concerns. When we have guests I always find people standing over it and having more fun trying to guess what all the things are for.
We also have ancestor altars with sepia photographs going back to the mid 1800’s of our great- great- grandparents looking down to photos of us.
We have altars on our computers. These reflect the things we care about when we are working. Mine has among other things my ordination certificate and several pieces of art I’ve done in various Circles.
I have a portable altar in the ashtray in my car, a few shells and crystal and an amulet for protection. Kwan Yin rides safely in a cup holder.
One of my students made me a wonderful traveling altar. A gnome dressed as a witch including hat and broom and she has a basket of plastic clay ritual tools. It has 5 tiny corner candles, a bell, a chalice, a pentacle, a wand made of a toothpick with tiny ribbons of embroidery thread and sequin stars. It’s one of my favorite things.
An altar at work can be as simple as an action figure or toy that represents deity and a shell and crystal. It could be a small medicine bag with things in it that only you know about.
You can have temporary or permanent altars. You can do a holiday altar. You can hide one on a wall shelf in front of your books if you aren’t “out” of the broom closet. They can be tiny or rather large.
You can make yourself a pocket altar in coughdrop box. Tiny things like birthday candles, matches, tiny shells, small bag of salt, tiny crystals. One of those goddess pocket cards or charms they carry in some metaphysical shops. You can add a few birthday candles and a safety match. Little things that fit in the box and mean something special to you belong there.
You can have a coven altar that gets set up when you have your Sabbats and Esbats.
An altar can be anything you want they are individual as to contents and to purpose. As long as it represents something special to you it doesn’t matter what is on it. And if you don’t care to have an altar you don’t have to have one at all.