There are several different types of dominoes out there. You can find antique born and horn dominoes, wooden dominoes and even the plastic dominoes that you can get in the game section of Target.
The two types I use are the wooden ones and the plastic ones.
I like to make mini collages with the wooden dominoes, which are about an inch by an inch and a half (1"x1.5"). When I say mini, I mean small. The dominoes above feature a Mexican cowgirl (I made her lasso out of thick button thread) and a wedding photo of my mother-in-law.
The plastic dominoes are inked with alcohol inks and then given a focal stamped image. I saw this technique in Margot Potter's new book, Beyond the Bead. I am not sure if I will make many more of these as the inks can be expensive and you have to be sure they are super dry and cured before you stamp the focal image or everything goes to heck in a hardcart. Also, the plastic dominoes are larger and heavier than the wood kind.
As always, I just keep looking for new ways to mix up my jewelry. I'll keep you posted.