every phone i've seen recently supports both mp3 and wav format ringtones, i don't know anyone who pays for ringtones though...
That's good, MP3 and WAV are easiest.
Would you pay 25 cents for a ringtone that nobody on the planet has (yet), especially if that ringtone was Bitcoin related?
There are usually two types of ringtones: Music ringtones and sound clips. Imagine if you received a call at a party or crowded room and some goofy cartoonish voice started screaming "Bitcoin" from your phone

Might it be a good conversation starter?
Would anyone here pay 25 cents for custom, original ringtones?