as written below this, this does not help for the memory issue. (see also ETC memory best practices)
Regarding holding images on a central directory you simply can use a path relative to the modes directory, which is expressed by the variable etc.mode_root. Example
This finds all png-files from /usbdrive/Modes//
for filepath in sorted(glob.glob(etc.mode_root + './*.png')):
Now we create a directory “Images” on the usb-drive and move all images to this directory. So we can access them like this:
for filepath in sorted(glob.glob(etc.mode_root + '../../Images/*.png')):
The first “. ./” shifts down from /usbdrive/Modes/MyMode to /usbdrive/Modes
The second “. ./” shifts down to /usbdrive
and from there we go into /usbdrive/Images
Hope this helps.