Even if the percentage was pretty good, I would only use it if it were 100% for windows, mac, and linux users. I HIGHLY doubt that they all have that fon't. Just make it an image. I'm sure the image wouldn't be more then a few kb.
I second the opinion to make images out of them. If your that worried about hits on the server its time to either upgrade or move to a new host. Providing a few images won't even cause the processor usage to climb on a good system.