Now that you have jailbroken your iPhone and installed openssh or similat you may want to update one of those 6 crappy sms tones to something cool. In the end you will overwrite a *.caf file on your iPhone.

Here’s what to do:

a) Go to iTunes, preferences, general, advance, import setting, set it to use aiff encoding [it likely says aac now].
b) Get the file you want to use in iTunes, right click and create aiff version.
c) Close iTunes.
d) Find the *.aiff, copy it and rename it to *.caf
e) sftp the file to /System/Library/Audio/UISounds on you iPhone overwriting one of the 6 sms-recieved files already there.
f) Reboot your iphone, go to setting and select the overwritten tone.
g) Go back to iTunes, preferences, general, advance, import setting, set it back to use aac encoding again [if you wish].