You could look in the thumbnails-preview folder which is at least human readable. The kobo-images folder has a mass of subfolders named 0 to 249 (I think 250 to 255 are possible but I've never seen them used). Inside those subfolders are other subfolders with the same naming. Inside those folders, you will see files with names ending in .parsed which are actually png files.
so:
kobo-images => 2 =>2 =>
Code:
- a5c9d5f2-a20b-4b21-9bf3-93e55618ea71 - N3_LIBRARY_GRID.parsed
- a5c9d5f2-a20b-4b21-9bf3-93e55618ea71 - N3_LIBRARY_FULL.parsed
or
Code:
- file____mnt_onboard_eBook_Vance,_Jack_Demon_Princes-_Jack_Vance_epub - N3_FULL.parsed
- file____mnt_onboard_eBook_Vance,_Jack_Demon_Princes-_Jack_Vance_epub - N3_LIBRARY_FULL.parsed
- file____mnt_onboard_eBook_Vance,_Jack_Demon_Princes-_Jack_Vance_epub - N3_LIBRARY_GRID.parsed