You can actually buy interior mounting aerials, but to be fair, I don't like the radio stations =P Does your headunit not have a USB, Aux or SD card input? Also I think it would look a bit piss if it was just smooth. =\
And as you say that, the postman has just posted my new xenon bulbs for the headlights, side lights and fogs!
Have to have something in that aerial hole or else you will ruin your headliner