Great news for iPhone lovers, now they can select any ring tone as SMS tone on their iPhone. I have already done this and it really works therefore I thought that to share it with you guys.
Download the applications listed below;
JailBroken Iphone any Version
IphoneBrowser Or Winscp
Respring - Download in Cydia or ICY (Optional)
DOWNLOAD
Important Note: In each of the zip file there are 2 formats of files. First is .MP3 this is the Original, so you can play it First before You Put it or Change your Iphone SMS tone. .CAF Format is for your Iphone.

Follow these steps to change your iPhone’s sms tone.

1^st, connect your Iphone to IphoneBrowser or Winscp
2^nd, If you are Already connected, Look For system > library > audio > UIsounds
3^rd, in this Folder UIsounds Look For this Format:
sms-received1.caf
sms-received2.caf
sms-received3.caf
sms-received4.caf
sms-received5.caf
sms-received6.caf
4^th, Don’t delete these files this is your backup just rename it as sample sms-received11.caf
5^th, Unzip the tones that you download and drag and drop the sms-received1.caf in UIsound folder.

6^th, Go to Settings Sounds > New Text Message > Click Tri-tone and the New SMS tone is Change.

You have successfully changed your SMS tone.

After changing the sms tone restart you iPhone.
Important Note: In iPhone there are only 6 SMS tones. Name as; Tri-tone, Chime, Glass, Horn, Bell, and Electronic.

Change the following SMS tones of your iPhone:
sms-received1.caf - Tri-tone
sms-received2.caf - Chime
sms-received3.caf - Glass
sms-received4.caf - Horn
sms-received5.caf - Bell
sms-received6.caf - Electronic