The Thumbnail Managing Standard (TMS) tries to define a unique, software independant method for creating and storing file previews (called thumbnails).
The latest version is 0.7, where the local thumbnail directory for usage on read-only mediums has been introduced:
The discussion of the proposal takes place on the freedesktop.org mailing list: xdg-list@freedesktop.org. The archives are also browsable online.
Nautilus since Gnome 2.2.
Eye of Gnome current CVS version.
libgnomeui-2.2.0 provides a simple API to the thumbnailing subsystem.
libpreview is a Gtk/Gnome implementation, which resides in gnome cvs but hasn't been officially released yet.
Version 0.6.1, where the subdirectory feature introduced by version 0.6 has been dropped:
Version 0.5:
Version 0.4:
Version 0.3: