According to a translation of the latest Famitsu magazine, Tekken Tag Tournament 2's character customization is going above and beyond what was seen in previous entries in the series.
"You can customize your character's looks with costumes, items and hair styles. Costumes can be set with color changes in specific areas. For hair, in addition to front and back customization, you can change sideburns and also equip hair accessories.
The game will offer plenty of items. You'll find over 30 per character. Some items will cause special actions during battle. For instance, if King is wearing a particular belt and you use a particular skill for your K.O., you'll see a special winning sequence."