* One ceramic tile, any size/color you want (I use the 11.5" x 11.5" size). You can get these cheap at Home Depot; they are actually bathroom/kitchen tiles.
* Acrylic paint in two contrasting colors (such as silver and black) and a few small paintbrushes (from a hobby store).
* "Clear acrylic sealer" in a spray can (also from the hobby store). It comes in GLOSS or MATTE.
* "White graphite paper" (also from the hobby store) if your background is going to be DARK; otherwise, get BLACK graphite paper.
* Self-adhesive felt pads (also from the hobby store). You're going to put them on the bottom of the tile so that it won't "clatter" and won't scratch your altar table.
If you're going to paint a color background on the tile, do this first and let the paint dry completely. This is the easy part. Go ahead and put on a couple of extra coats; allow one hour drying time between coats.
Come up with a good picture of a pentagram, in a size slightly smaller than your tile. You can grab one off the web, capture it to your hard drive, and use a graphics program to change the size. Once you've sized it, print it out.
Position the graphite paper CAREFULLY onto the now-painted tile. Position the pentagram printout CAREFULLY on top of it, in the position where you want it to end up on the tile.
Tape everything into position (don't let the tape touch the painted surface!), or clamp it down. Then, using a ballpoint pen, "trace" over the lines of the pentagram. This will leave an impression on the face of the tile itself.
Remove all paper. You now have a faint line-image of your pentagram.
Now comes the hard (and tedious) part: using a small paintbrush, fill in the lines - paint the pentagram itself onto the tile, inside the lines you just "graphited" onto the tile. If the pentagram itself is a LIGHT color (such as silver) and you're painting on a DARK background, you'll need at least two coats.
After all coats of paint have dried thoroughly, spray on the sealer.
Decorate further according to your own artistic flair. Attach the felt backing so that the tile won't scratch your altar. Alternatively, you could attach a hook so that the tile could be hung on a wall (you'll need to use JB Kwik).