Okay, somebody correct me here if I'm wrong.
I was under the impression that a regiment usually carried two flags, if both were available. One was the national flag. The other was the regimental flag. The regimental flag was specifically designed for the regiment, and often incorporated some aspects of the national flag, with the regimental number sewn in prominently, and perhaps a motto or another state symbol attached.
Due to battlefield confusion, the Confederate Battle Flag was often substituted for the Confederate national flag. And often the regimental flag would have some elements of either the national flag or the battle flag incorporated in it (depending in part upon when the regiment was created).
But this picture appears to be a Confederate Battle Flag without any particular regimental inscription. It may have been the replacement for the "national" flag for the regiment, but wouldn't there have been another regimental flag, peculiar to that regiment with some special identifying marks?