Mercy Brown is now the subject of a young adult novel. A (fictional) modern young collateral descendant of the unfortunate, mutilated Mercy researches her relative's life, which helps her deal with her own problems. There are some elements of the paranormal in the story as well, which I guess would make it a good Halloween read.
Some names and ages of the principals were changed (her dead sister is called "Grace" rather than "Mary Olive"; the afflicted brother in the book is a young boy, while her brother was in his 20s and a newlywed.)
http://bangordailynews.com/2011/10/21/living/meet-the-last-new-england-vampire/Apparently there are no photographs of Mercy or her family from that period (1880s-90s); at least none have surfaced at this time. However, Mercy did leave a souvenir of her life, talent, and interests in this handmade quilted coverlet, which was preserved by her father's side of the family:
http://www.quiltindex.org/fulldisplay.php?kid=4D-85-35