You can get a lot of ideas at:
If you don't like the look of the glass, you can always cover it with contact paper or temporary wallpaper. You could also use Looking Glass spray paint and a mixture of vinegar and water to create a mercury glass look. Frosted spray paint could look nice, too!
Are you asking how to decorate it? or fix scratches? One thing might be to buy a frosting spray paint at a local hardware store. Remove the glass and spray in a clean area. Don't overspray the area. When dry - return the glass to the table.
Put under the glass some dried flowers or pictures of your life tell a story
For a quick and easy application that is not permanent (styles do change), you should look at "film" that comes in a large variety of colors and is easy to change out at a later date. It comes in plain to the colorful cut glass look. The good thing is you can put it on the underside and will no have to worry about anyone ruining it at a later date.
It is inexpensive and not messy to deal with! No brushes to clean!