The Diamond is widely known as the 'love' stone-which is why it is the number one stone used when becoming engaged to be married.
it symbolizes peace, fidelity, and serenity. and, the reason it is worn on the third finger of the left hand, is because of the vein that runs directly to the the heart.
other stones to consider however could be:
rose quartz--one of my favorite stones! it is known as the crystal of love also. it can bring unfailing loyalty in love, and long term relationships. it is a calming stone in nearly any situation and is one that brings peace. a very good stone too, to calm your nerves, if you are anxious. might be a good one to consider!
a moonstone. a very pretty stone that is suppose to stimulate love and happiness. it is also known to protect the love you have between yourself and your partner. is especially good for the people born under the sign of Cancer.
Opal is another great stone, as it stimulates love and passion. another beautiful stone too.
sapphire--is suppose to be a lucky stone, and is also a good choice and one that is given often as an engagement ring. it is known to keep a marriage happy and also symbolizes faithfulness.
aquamarine symbolizes honesty and loyalty and can ensure a long, happy marriage.
garnet symbolizes faith, honesty, grace, loyalty and fidelity. it is also known as the passion stone.
ruby-symbolizing success, devotion and the passion and promise of love.
there are, I'm sure countless more. perhaps picking a few of these and putting them into a little silk purse that you can attach to your wedding dress would be nice.
I would suggest you find a crystal and gem book or information online and find what you like to include on your wedding day.
Congratulations!