Leox Graphite icon set contains 50 folder icons to replace at least the system folders. The icons have a cool graphite (grey) look with embossed pictorials. 512 x 512 pixels icons for Leopard 10.5.x included.

Icons in this set: applications, burn folder, classic, desktop, developer, documents, dropbox, generic, group, home, library, movies, music, open folder, pictures, private, public, read only, sites, smart folder, system (apple), users, amsterdam (xxx logo), backup, bookmarks, code, discs, download, emails & letters, favorites, feeds, fonts, helpful, ideas, manuals, notes, podcasts, podstuff, scheduled, sounds, sync, system (linux), system(windows), toaster, todos, toprated, caution unchecked stuff, uploads, utilities, vintage