"Pic" is a hideous abbreviation and should be avoided.

I used to work at a small-town weekly newspaper. My boss, the publisher, came up through ad sales, not editorial. Many, many folders, bore "Pix", not just "Pics." He also liked "Thanx."

Once, he made a form e-mail and wanted me to send it out with my name on it. I made him change "thanx" to something resembling English. He really didn't like my snooty ways.