In this article from Martha Stewart's website, she shows how to stencil a clock directly onto a wall. I loved this idea, and decided to see what clock stencils might be available to speed up the process. A quick search found several possibilities, of varying sizes.
This Cross Hall Clockface from Designer Stencils comes in 12" and 22" styles. A similar clockface without the decorative corners is available in 22", 30", and 36" sizes.
Jan Dressler's Parisian Clock, is shown left.
iStencil offers a variety of clock stencils in various sizes.
For a more whimsical look, try Stencil Planet's Melting Clock.
And last, but not least, here's a classic clock face, shown left, from The Stencil Library.