I think I had found out the root cause why some of you when updated to 3.1.2 with Jailbreak will not able to get the logo. If you use Pwnage tools without upgrading the baseband (upgrade from 3.0.x to 3.1.x), you will not get the logo. This is the first time when I upgraded and couldn't get the logo and need to use SSH to transfer the file manually.

Yesterday, I upgraded to stock 3.1.2 from Apple, then run Blackrain to jail break. After it's done, I use the Pwnage tools custom firmware 3.1.2 to update again (I heard there is still some problem with Blackrain RC2 when running certain custom program). Restore and install ipcc file. The logo is there and my baseband is 5.x.xx. For those with Maxis set, should be no problem as our set is unlock. For those getting from overseas, please don't use this method. You can't upgrade 4.x.xx baseband to 5.x.xx or your phone wouldn't unlock.