Before the existence of Zeppelin in Cydia which lets you set custom carrier logo, we did a tutorial on how you could easily do this with the help of SSH or iExplorer. Both the methods would work, but this tweak makes it a lot handy for you. However, not all custom logos are available in this tweak which could be added manually using both methods.
Many popular custom carrier logos like batman, superman, Assassin’s creed etc are available. Once you have installed Zeppelin from Cydia, it would not add any extra icon on the springboard. Instead, you need to apply and respire from the settings after choosing the desired custom logo. Please note that for the changes to appear on the status bar, respiring is necessary.
Despite of custom carrier logos, the developer has called them themes. Zeppelin is available under ModMyi repository for free. All you need to do is to search and install the tweak. Let us know if you face any issues in the comment section.