.tnb is Bitmap picture image
Key Features: .TNB File Extension
What is an .TNB file?
It looks like files with tnb file extension might have been used for some old bitmap image format. Probably no longer used or obsolete, or simple error.
No further information could be found.
This tnb file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.