Just throwing my two cents out here...Sorry I'm not directly answering your question, but I was thinking of the pre and post time skip picture issue over the weekend. Since Q takes up 33% of the Rebuild series so far, I think there really has to be a post skip picture somewhere in the bio box. I like your idea of the collapsible image, but I was also thinking of adding the post time skip image to the bottom of the box, kinda like how Wikipedia will have an alternative album cover under the info box for an album... http://en.wikipedia.org/wiki/What_Difference_Does_It_Make%3F
Also, there's the option of jamming the pre and post time skip images right next to each other in the bio box, but I don't think that would be too aesthetically pleasing....