NOTE: When I revert back to original logo, it appear broken although md5 of the logo is correct.
And this method only change Welcome message logo but not F5 logo after you login
Log in to the BIG-IP command line.
1. Remount the /usr file system in read-write mode by typing the following command:
#mount -o remount,rw /usr
2. Change to directory logo_f5.png
3. Backup F5 default logo
#cp logo_f5.png logo_f5.png.orig
4. Upload similar sized logo that you created give it name (“logo_f5.png”) to the same directory, You might want to use WINSCP.
5. Check your login page it should be changed.
6. Modify the file held on the /usr file system.
Remount the /usr file system in read-only mode by typing the following command:
#mount -o remount,ro /usr