Now the USPS is part of the federal government, despite their claim to be "private enterprise". They say you can use "any" picture on your stamps.
This could be your opportunity to send out mail with Hillary on a broom, or Bill behind bars, on 3 cent stamps. Or "W" stamps, a great idea if you're working for Dubya and are doing mailings.
I didn't look at prices, but you buy blank, high-security pages of stamps, and then print your pictures and bar codes on them. You have an online account with money in it, and each stamp value you print is deducted from it. It's a convenience, and maybe a way of getting something noticed. At least by the postal inspector, who carries a badge and a gun, something not issued to UPS or Fed-ex.