Decide on your image.  There are a few ways to go about this:

Use AI to design your image

Buy or choose a free image

Create a drawing and trace it in XCS

For this image I looked for free coloring pages as they make perfect line art for engraving

Import your image into XCS

Use the cameras to line up your tile and image

For ceramic tiles I use 60 power and 200 speed.  For these tiles that are around 4" it takes 3-5 minutes to engrave depending on the complexity of the image

After engraving, spray a little alcohol on a paper towel and wipe of the surface of the tile to remove smoke and debris

I've seen tutorials that use alcohol inks like Sharpies, etc.  Unfortunately, the glaze on my tiles is too porous and the ink kept staining the tiles so that was not going to work.

I did find a good solution though.  If your tiles are similar, paint them generously with acrylic paints.  I used a few different brands and they all worked well.

Let the paint sit for 1-2 minutes to dry a little bit.  Then rub the tile with a paper towel to remove the excess.  If all of the paint from the engraving comes off you did it too soon but you don't want to wait too long or it gets hard to remove.

If you find that some areas are not colored enough you can repeat the process.

Enjoy your new coaster!