Backrounds are the bases for tollgraphics (look side XX), details and plat-
forms could let the pic looking more interresting and complex.
In this example the white brushes over the cuts were used as base. Now the
instructions for the GFX on this page:

1. You may not use colour-range. The already active ones
   have to be deleted (So Dpaint can also shade brighter with the backround
   colour).
2. Draw an one-coloured brush and lay it with shade (F5) on the background.
   After some time it gets brighter (depending on how often you shade on
   this place.
3. If you want something like the effect in pic #3, then you should start
   in the middle, and then go to the outside, quite fast.