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
Heartless/Hiruma--...Hiruma would be using them for blackmail and world domination?
Larxene/Porn--(shh, I needed something to even out the numbers so it was either Porn of shoddy-representation-of-self, and that would have been scary) ANYWAY. Uh... Yeah.
Saix/Vexen--Why looks, it's my OTP. What a coincidence.
Xaldin/Xigbar--:O My other OTP. What needs to be said?
LAWLS I'M INTERESTING WUT.
...this is what happens when you leave me alone, Jo, I do STUPIDITY.