Poolga offers beautiful iPhone and iPad wallpapers created by illustrators from around the world. They are free and a chance to look at something lovely every time you turn your device on. I, of course, gravitated to all the illustrations that featured pencils and various office supplies but visit the site and peruse because there is all sorts of fabulousness to be had.
From left to right, top to bottom:
Stuff on White by Andrea Manzati, Pen by Denis Carrier, Pencil Gold by Thom Lambert, Letter by Louis Reith, Toolbox by Christopher Monro DeLorenzo, Workaday by Luke Séguin-Magee, Draw by themeekshall, Enforcer by Dale Edwin Murray, ¡Uops! by Júlia Solans, 009 by Kitchen, Brainstorm by Dan Gneiding, American Typewriter by Tom Davie, Moleskine by Luis Mendo, Having it All by Matthew Walkerdine, Mobile Office by Rainer Berg
I almost forgot one of my favorites:
Paper by Frank Chimero