It's reaching that time. Practically speaking, it's a good idea to start on covers and book summary's when the manuscript nears completion. The final cover may not quite look like this, but it will probably be close.
The cover image is an excerpt from "Self portrait in a straw hat" by Elizabeth-Louise Vigee-Lebrun. She was a talented painter in late-18th century France. I actually found her self-portrait while researching opera singers for a cameo in Charlotte. The cover image could have been:
Her facial expression really invokes Charlotte's naivety, and the fashion is correct for the time, but I think Ms. Vigee-LeBrun makes for a much more appealing image.