So I was thinking that it would be a nice cosmetic change to assign guild members different ranks based on how much reknown they have earned for the guild.

Something like:

Greenhorn: 0 to 10,000 reknown
Scout: 10,000 to 100,000
Lieutenent: 100,000 to 500,000
Captain: 500,000 to 1,000,000
General: 1,000,000 to 5,000,000

And so on. It might be a nice little bragging rights thing. Might also encourage greedy guildies to take tales of valor as a end reward every once in a while...