[Vet]

The banner registry key is:
HKEY_CURRENT_USER\Software\Valve\Steam\LastCo ntentProviderURL

It usually a URL that points to the last banner used. It is NOT what's being changed to display the types of banners being shown here. Those are displayed by using custom .res files in the resource folder.

You are free to customize these settings on your own machine however you want. It is not slowhacking. Slowhacking is when a plugin or admin changes your settings (usually maliciously) without your knowledge or approval.