The themes in Nuke6.5 work together from the themes folder.
You do not change the Style(template) setting under the Forum admin ANYMORE.
Leave it at subSilver always.
All themes get uploaded to your themes directory, NOT your modules/Forums/templates directory. The only thing in there should be subSilver.
You change your themes form Your Account page Theme Selection Only.
If you use matching themes like on this site, then your Forum tempalte will change when you change the theme under Your Account.

mikem