Borrow inspiration and color ideas from design periods such as Art Deco, Jacobean, Elizabethan, French Impressionism and Imari. Prep the glass surface with a sealer, Mod Podge or a matte primer and allow it to completely dry. These products for painting glass are available at craft stores. Use tempera, acrylic or enamel paint. Apply several coats of varnish when you're done. This will protect the paint and keep it from chipping.
Affix lightweight mosaic tiles, plastic beads, cardboard puzzle pieces, ribbons, fabric, wallpaper, buttons, silk flower leaves, faux jewels and photographs with a strong glue or an epoxy adhesive. Create a decoupage effect with pictures taken from magazines, newspapers and catalogs. The only cautionary note is that if you intend to use the decorated jar as a candleholder, the heat will cause the glue to melt.
Fill your glass jars with elements that will form distinctive layers of color. Examples include rocks, shells, different types of dried beans, colored sand, buttons and beads, marbles, candle wax, colored bath salts, potpourri, mini ornaments and bulk spices.
Use glass jars of different heights and shapes as the foundation for characters and simple animals. Purchase Styrofoam balls for the heads, yarn for the hair, pipe cleaners for arms, wings, antlers or halos, sequins for the eyes and felt or other fabrics and trim for their outfits or fur. Use cotton padding to add definition and shape. These jar sculptures can be used as centerpieces or the creative covering of a gift of cookies, candy, bath salts or a small toy.