You have a few options when determining your namespace for themes. You could use: 

  1. Oqtane.Themes.YourThemeName
  2. Oqtane.Themes.YourCompany.YourThemeName
  3. YourCompany.Oqt.YourThemeName
  4. YourCompany.Oqt.Themes.YourThemeName

...and variations thereof. 

Important: You cannot really use YourCompany.Oqtane.Themes.YourThemeName! This would be a obvious choice, but it won't work. 

The reason is that if your custom namespaces contains anything with Oqtane, then your .razor files can never access the global Oqtane.xxx namespace, because Oqtane.Something would always be regarded as YourCompany.Oqtane.Something. This also cannot be fixed using global::Oqtane, as global:: is not supported in Blazor