A painting's background, as essential for the final results as the motive itself.
This applies both to "conventional painting" in oil and pastel as to painting in pixels.
I usually use a tone of gray pink for landscapes and gray green for figures
and portraits, generally avoiding black and white as a background for my paintings.
The obvious reason for that is that the constrast of the colors in relation
to each other is easier to evaluate against a more "neutral" screen than black or white.
The example below tries to illustrate this, the few brush strokes of this just
begun landscape melts easier on the gray pink area to the low-left part of the picture
than against the black or white areas. The flesh colors on the
face appear clear against the gray green on the low-rigt part of the picture
My suggestions about how to choose the background of a new picture:
Avoid painting on black or white (unless, of course, if you are using water color).
Try a shade of gray pink as a background for landscapes.
Try a shade of gray green as a background for portraits or figures with flesh colors.
Another example:
Observe how the same colors appear against the four differnt backgrounds.