Your custom scheme might require the use of custom background images.
SysAdmins must copy custom images manually into the proper directories on the filesystem.
Best practice: Have your custom background use a location and a naming convention.
BACKGROUND-IMAGE: url(../images/customscheme/SCHEMENAME_STYLE.EXT)
Example:.
BACKGROUND-IMAGE: url(../images/customscheme/acme_userhead.gif" )