@dimok
I've been posting in the USB LOADER COVER IMAGES thread about the possibility of auto resizing the covers to work with loaders such as yours (image dimensions multiple of four). The author of the covers website
http://www.theotherzone.com/wii/ djtaz thinks this could be added quite easily and I think this would be a perfect way for you to access your covers. No packs to download, no sizes to change, just fire off a custom URL to the site with your required dimensions and it would do the rest, maybe he could even host the disc covers if you can get them together.
Currently, they use the full title ID, but I have spoken to him before about a four letter system (not three, as the covers are different between regions, especially when it comes to NTSC-J and the rest of the world). He said that if the coders would support it then it could be changed, this would stop some of the duplicates on the site. Either way, this does not affect SD usage or the end user, only the uploaders (multiple uploads for the same game due to last two digits). As far as I know, the last two digits refer to the disc pressing, perhaps the production run.