Neat ideas....

I found these ideas at http://weddings.about.com/cs/style/a/unityceremony.htm

Celtic Oathing Stone
"The couple holds or puts their hands on a stone during their vows to "set them in stone" (I also believe this is where this phrase comes from, or so the rumor goes)."

Truce Bell.
A bell is rung on the wedding day, the happiest day of the couple's lives and then is placed in a central location in the home. If the couple starts to argue, one of them can ring the truce bell, reminding them both of that happiness and hopefully ending the disagreement quickly.

I found these at ::::: http://www.celticcolours.com/weddingtraditions.aspx
The Marriage Bell

Celtic tradition has it that every young couple should receive at least one bell as a wedding gift. The bell is placed strategically in the newlyweds' home, visible to all. When the inevitable argument or disagreement takes place one of the couple may ring the bell to end the discord and declare a truce without an admission of guilt or fault.

Bridal Bouquet

Tuck a sprig of shamrock into an Irish bouquet or a branch of white heather for the Scottish. Each thought to bring good luck.

Irish Horseshoe

To be sown into wedding gown or the be tucked into the bridal bouquet. The horseshoe has always been associated with good luck because of the level of importance the Celts placed on their livestock, particularly their horses.