Make a list of all the characters in your icons. (Although you may have more than one icon of a single character, they only go on the list once.) Alphabetize it. Take the first two people on the list; that's your first pairing. Second two people; second pairing. Etc.
I only have 3 icons...T^T
Sanzo and Tohma? A pair? Haaaaaaaaaaa that would never happen in a zillion years. XD
And I love my Yusuke/Puu icon to death, but I swear it's going to drive me mad.