Clytemnestra After the Murder (1882), by Hon. John Collier (1850-1939).
Most reproductions don't quite catch how much blood she has on her - this does become a lot more clear if you see the original. That red isn't part of the dress' pattern.
When I first posted the picture, there was a debate over the femininity, or lack of it, of the model for Clytemnestra. I subsequently come across the following in the Guildhall Art Gallery's booklet on Victorian Pictures:
While this dramatic image generally reflects Collier's interest in the theatre, it may have direct origins in a performance of Aeschylus's Agamemnon given on June 3 1880 by Oxford undergraduates at Balliol ... In this the part of Clytemnestra was played by a man - perhaps the source for Collier's unsettling, muscular figure.
So, there you are.
Then, here is the Great Torc from the Snettisham Hoards, which is on display in Room 50 of the British Museum:
An article on the Hoards from Current Archaeology can be found here, whilst here and here are two pages from the British Museum's website, one on the Hoards and one on the Great Torc.
(Click on the photos for sources and more information.)