Not sure I've posted on this subject regarding this issue in an individual post. Caching of covers in Kodi is part of the 'magic' and there is some sort of pre-fetching going on so that when you enter movies, it starts at the chosen pointer (title sort or whatever) and displays those items on the first page. Looking at any folder you will note that the content list out as fast as the hardware you are using, give 1000 files in that folder and the display will be sluggish at best, put 100 files in it, and bang the listing is magic. The same goes for the structure within Kodi, you have 1000 movies and want to see them all in one shot.. and then we enter the issue of the cover fetch in the thumbnail folders, and points in your library matching up the images with the listings, sure computers are fast and some of this is pre-cached, flip the views to some new way of viewing and Kodi has to rebuild that view with thumbs to fit. I've got a fairly large folder, 400 listings and in cover-flow view alphabetical sort, the first page loads up directly, but subsequent the last page is blank covers for a few seconds when spinning through the collection, I can actually see the covers load sequentially. Exit and return, and you're looking at the cached covers and they're magically all displayed. Change views and it starts all over, the cache will fill over time with usage and it will speed up.
HOW-TO:Reduce disk space usage (wiki) If you have not made an advancedsettings.xml file before, see the example in the wiki #Limit the size of cached images.
Then we get into artwork that can be very large arbitrary sized artwork to be displayed, so some consideration for standardizing your graphic files is good. Think about disk, logo, fanart, posters, actor images, extrafanart, thumbnails, clear art, loading for each listing. Even small listings can become much larger, not to mention fragmentation of the cache as new listings are added (the issue in most of the above posts), This link is useful iin offering solutions.
http://forum.kodi.tv/showthread.php?tid=...pid1556148 Milhouse and his texture cache maintenance utility
http://forum.kodi.tv/showthread.php?tid=158373 I do want to add, that once in a blue moon I go through my thumbnail folder in icon mode, looking for corrupt images and do find a few (how these get corrupted is unknown) but it will explain some cover issues. And one last recommendation-
http://forum.kodi.tv/showthread.php?tid=272112.
Suggestion:
Export your library to separate files (ensure that each video folder has the correct meta-data)
Remove your source(s) in file mode.
Clean library (ensure not files are listed)
Re-add your source, choose 'local information only', as your scraper.
Scrape local information (at least you will have some organization)
Change Scraper back to chosen default.
most of this can be accomplished with texture cache maintenance utility
http://forum.kodi.tv/showthread.php?tid=158373