Arcana. Especially her before-last profile picture, the one with the magic swooshes around her. I purposely didn't raise her affection to the maximum, because I don't want to change that image. I might do the last part of her affection quest if we get to pick which of the images we want shown on the harme page, instead of automatically getting the "most nude option".
Oh, and I also love Bunny's bathingsuit. She's another girl I didn't upgrade, simply because I don't want her to loose that suit.