I've looked and looked for a flag later than the one captured at Murphreesboro with no luck. The Civil War Flags Message Board is a very good source, but they can only come up with a surmise that the 25th probably carried a standard Confederate battle flag until the end of the war.
I created a piece of art (ala Jasper Johns) that is a first national flag with 25th Ark. Infantry lettered on it. If you run across that painting it is pure fabrication.
Also I have created (in PhotoShop) a standard battle flag with battle honors (also purely invented) that I could show you when I return this coming weekend. The latter is my idea of what such a flag could have looked like.

for Jasper Johns type painting see:
http://www.urbiedixon.net/images/DuchampsFlag.jpg