The Media ContentPack is used to add files to the final Media or ISO, for example an AutoUnattend.xml
Directories within OSPoshMods are created by default and follows this logical assignment
Media\ALL
Universal Content
Media\$Architecture
Content for a specific Architecture
If you want to add content to the root of your Media, simply add it to the proper Media ContentPack
New-OSBuild -SkipTask -Execute -SkipComponentCleanup -SkipUpdates -CreateISO