what is the function of "what" in this sentence?

[miladhazraty]

hi
In this sentence :

the surrealistic moment in art in the 1920s ans 1930s placed an emphasis on what is pictured dreamlike images.

what is the function of "what"?
if "what" = question word, way this sentence ended with "."?
if "what" = relative pronoun, !?
if "what" = relative clause? why come verb after what?

thanks.

[Alan]

It is a NOMINAL RELATIVE PRONOUN (= "that which")