There's some discussion as to this picture by William Rimmer (1816-1879). Titled Evening (Fall of Day) it would seem to be a metaphorical depiction so literal as to make little sense. Day does not actually die in our Western mythology/symbolism, despite the common turn of phrase. And why is the figure haloed and lacking in genitals?
It makes more sense if you see the figure in relation to the fallen angel Lucifer - "Morning Star" or "Daystar" of Christian mythology - which is loosely based on Biblical references, but mostly fleshed out in Milton's Paradise Lost. Rimmer would have been familiar with that work.
Here's a statue of Lucifer on the Fountain of the Fallen Angel in the Buen Retiro Park in Madrid, situated at 666 metres above sea level and very similar in realisation.
|Ricardo Beliver 1877|
You can read about the occult hoo-hah surrounding their album Led Zeppelin IV, here.