Accessory Combinations

-Flower crown
-Flower Glasses
-Flower Necklace
-Petal Wings =60% Cute Voltage

-Electronic Operating Panel
-Cyber Visor
-Equalizer
-Speaker =60% Neutral Voltage

-Demon's Head Wings
-Skeleton Eyepatch
-Chained Necklace
-Fallen Angel's Wings =60% Cool Voltage

-Jewelry Hair Ornaments
-Face Veil
-Gorgeous Necklace
-Jeweled Cloak =60% Beauty Voltage

-Hat with Feather
-Lucky Clover
-Ocarina
-Accompanying Musical Instrument =60% Choas Voltage.

 

EDIT: Oops, PinkoStickLuv got it already :)

Neutral - Cyber Music

Head - 電子操作盤 (The green electronic band around the head)
Face - (The big metal visor with the green beam in the center, it's somewhere halfway down the list)
Chest - イコライザ (The green equalizer beams in the front)
Back - スピーカー (The floating speakers)

Cute - Flower Fairy
Head - 花の冠 (The flower crown)
Face - 花のメガネ (Flower spectacles)
Chest - 花の首飾り (Flower necklace)
Back - 花びらの羽根 (Flower wings)

Cool - Fallen Angel

Head - 悪魔の頭羽 (The devil wings on the head)
Face - 骸骨の眼帯 (Skull eye patch)
Chest - 鎖の首飾り (Chain necklace)
Back - 堕天使の羽根 (Black angel wings)

Beauty - Beautiful Princess

Head - 宝石の髪飾り (Gems on the head)
Face - フェイスベール (Purple veil)
Chest - 豪華の首飾り (Golden necklace)
Back - 宝石マント (Purple cloak)

Chaos - Wanderer(?)

Head - 羽根つき帽 (The big ass, green hat with a feather)
Face - 幸運のクローバー (Lucky clover in the mouth)
Chest - オカリナ (Ocarina, the brown looking instrument with lots of holes in it)
Back - おともの楽器 (The brown looking "Chinese" guitar on the back)

These should be the highest for their respective elements. I've found some, like Robot Maiden and Graduation but they aren't as high (only 10%/12%)

 

There's actually a second Beauty Accessory combination that gives 20% - pretty useful if the beautiful princess one looks too darn weird in sacred spear explosion boy :P
I can't translate the name of it, but:

Head - Either Gold or Platinum Crown
Face - Butterfly Mask
Chest - Golden Necklace
Back - Butterfly Wings

 

The name is "Butterfly Princess" which is as sexist as it can be.