This is raw, not sorted and not complete tutorial, which we got from ilove3D (BIG THANKS!). It will be updated and cleared soon. It is not tested yet!:

"When you flash the sbf, you can see there're many smg files in the same folder try copy them to another folder ( it will disapear when flash finished or rsd closed)
1. The cg34.smg is picture, ringtone, power up off image, and so on icons
2. The cg37.smg is secure setup ( notice that has 0x1000's FF head file, delete it first when modding). It's important because the flexbit in it
3. The cg39.smg is boot logo(not the poweron image,but before it), it simply contains 2 gif image, see the
post:http://moto.it168.com/viewthread.php?tid=31206
4. The cg41.smg is usr/language , so we change fonts here
5. The cg42.smg /usr/setup , some setup config files
6. The cg43.smg / , main file system, the bin, lib, the SYSqtapp ( 0x1000 FF head file)
7. Beside cg39.smg, the other cg34 cg37 cg41 cg42 cg43 are cramfs file systems, you can mount -o -loop the smg in linux(root)

# tar zcvf xxx.tar.gz mountedsmgfolder
# tar zxvf xxx.tar.gz -C targeteditfolder

so you can mod the files in target edit folder then

# mkfs.cramfs targeteditfolder/xxx cg##.smg

so you made a new cg##.smg yourself
You can overwrite the smg content in sbf, be carefull the 0X1000 ff head file, and the origin size of smg , plast FF to your new smg to make the size the same
Make the sbf this way will failed when flash finished ( but it works, it really flashed into your phone), because there're checksums in the position 0x300 ~ , 2 block the end of each line
Use checksum.exe to see the checksums( if you got the value EC FA, it should write as FA EC, it must be the opsite of checksum.exe value)
Overwite the checksums, flash will be perfectly finished"