Apparently DC also has(or used to, depending on whether it still does or not) its own omniverse as well :
http://media.comicvine.com/uploads/9/98086/1821486-1762275_adventuresofsuperman617fi2_super_super.jpg
Originally posted by Galan007
DC is currently classified as an Omniverse. It was specifically referenced as such fairly recently in Red Hood and the Outlaws, as well as Superman.The scan you posted above is the only instance I know of in which an Omniverse was referenced in pre-Flashpoint continuity, though.