Whenever a client looks at me like I have six eyeballs, just because I've presented them with a radically new idea, I immediately pull out my secret back-up plan- The Peace Symbol.
"Oh, yeah, well, what the hell does the Peace Symbol mean?" (I'm usually more diplomatic than that MOST times...) It's almost fail-safe. The client pauses, realizes he has wholeheartedly accepted a mark into his life that makes absolutely no sense graphically. But it's there, it's a part of his culture, and it's so universally accepted that it's become a part of the ubiquitous language of symbols. And unlike a dove, or a bomb with a circle and a line through it, it's totally abstract. Its' design means no more than a red octagon means stop, but we've accepted that symbol long ago, too.
I'm currently designing a set of icons for a new piece of software that will be unveiled next year. It's a challenging assignment, because I am charged with solving a paradox- I need to create a set of icons that are unique and new, but that look like all of the other icon sets (so that people know what the symbols mean)! The problem with this rationale is that it presupposes that the software does things that already exist so I can simply re-draw existing icons in a new "style"—which isn't true! It does wildly new things, and consequently needs new icons!
So what does it take to convince someone to adopt a completely new icon- that doesn't exist already? Answer: a trusting client. Seriously. People want what already exists in the world. It happens time and again. This is particularly obnoxious in the logo industry. A short anecdote: The nike swoosh was finally accepted in a clumsy debate- the elegant mark survived because its' antagonists grew tired of fighting against it and simply threw in the towel. What did they really want? Stripes. Adidas had them, Reebok had them- it was the shoe thing to do. Thank God Phil Knight had some faith; that paltry $35 design netted billions of dollars for the company.
In the past, another icon solution was to use a really outdated shape. For instance, in Microsoft Word, the icon for "Save" is a floppy disk. That form is so old that I'm sure an entire generation of users doesn't understand it. Or an email icon that's a mailbox- an old, physical product is used to depict an ethereal space. These images are cultural archetypes that are embedded in our memories; designers can harness those memories for great success.
In my case, I designed the icons around clichés and idiomatic expressions. So though the designs may not initially be understood well, once they are learned they are incredibly easy to remember because their is a story attached to each mini-picture. Edward Tufte would describe this as "learning the key."
And as for the peace symbol- it's actually not an arbitrary shape- the design is a highly abstracted version of the letters N and D- which stand for nuclear disarmament. In semaphore the letter "N" is formed by a person holding two flags in an upside-down "V," and the letter "D" is formed by holding one flag pointed straight up and the other pointed straight down. Those two overlapping shapes were circumscribed to create the anti-nuke mark, which eventually because synonymous with peace. It's quite elegant and easy to recreate, which is probably why the mark caught on. You can learn it, just like my icons- well, hopefully.
In the end, everyone always loves the "new, fresh ideas" and grumble a little "why didn't I think of that?". Unfortunately, we think of things like that all the time- but our clients are too afraid to take risks, so we just reinvent the wheel, over and over again.