Inserting a background image in the editing blocks.
PermalinkThanks.
otherwise, maybe you're using a default them:
/concrete/themes/default/typography.css
or perhaps you've got a theme that you downloaded as a package:
/packages/your_themes_package_name/themes/your_themes_name/typography.css
/concrete/themes/default/typography.css
body.mceContentBody { background-color: #222 }