unknow files in books after database restore

[Anders]

I've had to restore the Calibre database because it was corrupt. Running a check afterwards, I found that all jpg and gif files in the book directories were ignored in the restore (other non-book file types like xlsx were not ignored). I often add alternative covers to Calibre, for example of the print version that I also own. I add them properly with the Calibre Add function, not just put them in the directory with Explorer, so originally Calibre knew about them and handled them as I expected (for example keeps them when I change the book title). Is there any way to tell restore to include these types (excluding cover.jpg), maybe by defining them in Calibre as user defined types? I don't feel like re-adding hundreds of files by hand, especially since April 2018 I frequently get the blue screen of death. I reckon this is not the last time I will have to restore the database. I used Calibre 3.20 [64 bit] in Windows 10 Home version 1803.
Afterthought: Perhaps make unknown files in books fixable in the library check function. The fix being the addition of the marked files to the database.