The Dark Chamber, paperback cover artist?

The first reprint (since its original publication in 1927) of The Dark Chamber was in mass market form by Popular Library of New York.  Though undated, it came out in October 1972. Here is the cover:

There is no credit for the cover art, but it's style looks somewhat familiar.  Anyone have any theories about who the artist was? 

Interestingly, the same art was used on the German translation of John Crawford's Dark Legion (1967), when it was translated into German in 1973 as Der Geisterhügel. (John Crawford was a pen-name of John S. Glasby, 1928-2011.) It has been suggested that the art is by UK artist Bruce Pennington, but Pennington himself has said it is not his work. Since the first usage of the art was on a US cover, one would suspect it was a US based artist.  

"On a Picture" A Cline poem from 1911, and its inspiration

Cline's poem, "On a Picture", was written in 1911, and published in Poems (1914). In Cline's own copy of the book, he noted that the inspiration was the 1887 painting "Empress Theodora" by Jean-Joseph Benjamin-Constant (1845-1902).  Here is the poem, and the painting.

 

                    On a Picture

Her eyes are like twin pools of silent waters

Within a forest, hedged by cypress trees,

At night, when all the tempests and the heat,

The white tumultuous heat of day, are over;

When night has brought her coolness and her shade

And the fair little moon, that climbs the heavens,

Reflected in twin images upon

The placid surface of the jetty pools.

 

And so the depths are hidden; only one

May look upon them, note the wavering moon

And all the stars of heaven there, yet guess

The sombre fathoms where move sinister tides

Beneath the perfect calm. And oh, the calm

Of those still eyes is like a thought of death!