PLEASE NOTE: I do not allow any use of my designs.
The first of three: as done in women's clothing.
Of the Christmas Ghosts, Past has always seemed to be something wispy and soft, airy and light. In the original text there is no gender or real shape implied, Past is a constantly changing, shifting form, which, to me, has always symbolized the massive amount of time that has/had been before.
Past is about nostalgia and memory, the parts of us that will always remember what was.
In this context, if the Dickens time period is "now," there would be no set time period reflected in anything representing Past. Parts of this design are Renaissance-inspired, some Elizabethan, and some medieval. There are hints of Victorian-ness here and there to echo the recent past as well. The cloth here would be very light, gossamer over silk or something of that nature, and multi-layered to create a "floating" look. Past has always been white and metallic to me as well, neutral, truthful even if it hurts.