We have a few options how to do it, (it also depends how many variants of images there are and if there are many duplicates)

Big folder called "images" or similar (in root or wherever it works, I don't know how you guys do this)
under here, images should be in sub-folders/directories based on size/origin directory.

How do we store it on Staticbrainz?
Would you want subfolders with the instrument name under the instrument folder?
i.e.
staticbrainz.org/../instruments/sarod/
staticbrainz.org/../instruments/sarod/thumb/
staticbrainz.org/../instruments/sarod/grayscale/

or one big

staticbrainz.org/../instruments/sarod.jpg
staticbrainz.org/../instruments/sarodplayer.jpg
staticbrainz.org/../instruments/sarodgreyscale.jpg
staticbrainz.org/../instruments/sarodgreyscaleplayer.jpg
staticbrainz.org/../instruments/sarodgreyscaleplayerthumb.jpg
(this seems a bad idea)

one big with subfolders like
staticbrainz.org/../instruments/sursingar.jpg
staticbrainz.org/../instruments/thumb/sursingar.jpg
staticbrainz.org/../instruments//grayscale/sursingar.gif
staticbrainz.org/../instruments//grayscale/sursingarthumb.gif
staticbrainz.org/../instruments/sarod.jpg
staticbrainz.org/../instruments/thumb/sarod.jpg
staticbrainz.org/../instruments//grayscale/sarod.gif
staticbrainz.org/../instruments//grayscale/sarodalt.jpg
(this is my preference but.)

etc etc (these depend on what images are actually under there, if there are many duplications etc. when importing initially, or as a cron-job after the initial import, applying some hash dupe-check could work (ie if image is hash-sum identical to another, ignore it.))