Ahhh.... interesting - please tell me how to rename....?
Also - what about propid 117 - 'File numbering (continuous=0, Auto Reset=1)' according to DanielF's ver helpful 'uBASIC' user guide.
This is the same as the canon number options in the menu, which should be described in your camera manual.
To rename in CHDK, you would have to use a lua http://chdk.wikia.com/wiki/LUA
script with os.rename.
A couple things to know
- if a file already exists with the name you want to rename to, you must delete it first. Failing to do so may corrupt your filesystem. Attempting to "move" a file to a different directory with rename can have the same effect.
- the camera sometimes gets a bit confused by file changes made through CHDK. I'm not sure if there would be any problem rename image files, you'd have to experiment and find out.