I got irritated by having 53024 as the carrier name, so spent significant time looking for the solution.  Found the ultimate which works great, and you can display whatever text you want.  It is called Personalizer 3.1 by CodyPPC.  Searching the internet you will find downloads for version 2.0, but look for 3.1.  It is available only on one PPC forum, can't remember which.  You need a login to download the CAB file, but just Google the forum name and "login" and you will quickly find freely available logins (I don't have a problem with that for only downloading one file from a site you might never visit again).

Installing is painless, simply copy it to your device and run it from your device.  Then find it under Programs.  Enter what you want to display, and that's it.  Some say it does not "stick" until you soft reset a couple of times, but on my Glofiish X610 with Win Mobile 6.1 Pro I never had to reset as it just worked.  When I turn on the display the text will briefly revert to the carrier number but within 1 second it returns to the text I've selected.

There is a registry hack involving adding a key for the carrier number, but that sounds like too much work for such a simple thing and I don;t care if I'm on a 2D or VF tower anyway just want something better than a number.

Apparently you can also create a carrier logo whatever you want with a 120x20 pixels GIF.  Will be playing with that next.