the background picture is not rendered, although visible in the interface. And at times it is also not visible at all. This happens with both Cycles and Eevee.
Shadowing is not consistent acreoos the 2 rendering engines. I.E. I intended to convey a shadowing effect whereas the cobra shadows would “snake” down the steps. This comes standard with Eevee but it does not happen with Cycles.
First, Eevee and Cycles are not the same! Despite what the add on Blender’s Website says, the two rendering engines have significant differences in their output.
Second, not all nodes work in Eevee! You can take a look at the User Manual to see which ones work in a limited fashion and which ones just flat do not work.
Third, not all of the new nodes work properly in Cycles, v2.8 is only in Beta and their still working on the nodes.
Fourth, Take a look at your camera’s clipping distance (located on the Camera Properties tab). Make sure that things are within view range.
Finally, Eevee and Cycles handle lighting, and thus shadows, differently. To put it mildly, Eevee is a Ford Fiat pretending to be a Ferrari while Cycles is a Rolls Royce pretending to be a Cadillac