1081 Graphic Workshop for Windows Thumbnail File Image (Raster) Image thumbnail files created by default within Graphic Workshop whenever a graphic file is written or updated. Can contain image, keywords and/or comment information. THN files are read by Graphic Workshop when it wants to display thumbnail images. The files themselves do not store graphics in any conventional sense. 1 Digital Preservation Department / The National Archives 20 Apr 2011 20 Apr 2011 fmt/336 PUID thn File extension 447 Graphic Workshop Thumbnail File Header ASCII: THNL 1 Absolute from BOF 0 54484E4C