Hall of Faces
This is the central registry at the Fools' Guild which contains long shelves of meticulously ordered blown eggshells, each bearing the painted likeness of an individual Clown, together with carefully indexed and filed descriptions, clothing, special routines, and so on. Unless in very unique and special circumstances, wearing the Face of another clown is an offence punishable by eventual death.
For a clown's face is his fortune. A dying clown can will it to a son, nominate a successor, or it may be auctioned by the Guild. The right to wear a famous Clown's make-up and costume and to use his routines can change hands for many thousands of dollars. As in the case of The Great Bazonko, who has been clowning for over four hundred years, the Face confers a kind of immortality. Indeed, Doctor Whiteface has been head of the Clowns for over three hundred years. The men behind the makeup may come and go, but there is always a Doctor Whiteface.
The Hall of Faces at the Patrician's Palace
There is a similar sort of repository at the Patrician's Palace. This is a place of quiet contemplation that enshrines the death masks of past Patricians. Or at least those for whom enough of the face remained, post-mortem, for a death mask to be made. Given the circumstances in which a Patrician may leave this vale of tears, some masks may only be partial, or else there are a mumber of empty spaces. From context in Making Money, it is fairly close to the Oblong Office, or at least on the same floor. Vetinari interviewed Moist von Lipwig here when there was a need for him to focus himself on the task in hand and not waver.