Qdig has many settings you can use to customize your galleries and each setting is briefly described using a comments right in the script.
The pages linked below provide some extra information about Qdig's settings. Most of the settings covered are common to Qdig 1.2 and 1.3, but some are specific to Qdig 1.3.
* = Ready for Qdig 2.0. Recent changes in Qdig have caused the documentation update effort to be restarted.