In my opinion, the game has a ridiculously low character limit for names. Especially since some of the pre-existing city names exceed the 15 character limit. So I made this little mod which increases the character limit for city, unit, and religion names to 99 characters to allow longer names.
It does not affect save games so even if you have used the mod to give longer names to cities/units/religions you can still load the save without it.
Spoiler some very long names :
I do not take any responsibility for you giving things longer names than the UI can handle without looking weird.
If you have any comments they are more than welcome in my Minor Mods thread: http://forums.civfanatics.com/showthread.php?p=13828280