The intense black/dark lining of the characters give a very special brand onto these paintings, a kind of cartoon characters, like Mickey Mouse , but not on paper, but in the space.
This style is very unique to Christoph, giving a strange but beautiful aspect to the characters.
The observation of a white background is valid, white is probably the worst background to give, because it darken strongly the colours to the eyes of the spectator and reader. Black emphasize the colour le most but is uniform.
Probably a light brown or creamy tone would reduce this contrast, that human eyes cannot withstand without reacting. To give normal colours, we have to lighten the picture and the white background will become so luminous that it will hurt the eyes, like looking at someone placed between the sun and yourself !!