In the past, I checked for these: images listed in the Ponibooru image info DB ("meta.sqlite") but not in the torrents or any collection of ponibooru.org images. I found multiple MD5-matching files, multiple heuristic-matching files, some other files, and multiple lost files. Today I did this: found image IDs which were deleted when Ponibooru was still around. 8368 images were found to have been deleted back then. 191273 images were not deleted. (191,273 + 8,368 = 199,641.) The file count in the torrents for the 4 ratings is 191,277 (7975 + 8405 + 166644 + 8253 and is a bit more than 191,273 due to readme files and whatever). Only one of the deleted images showed up in the SQL file:
>$ cat poni_del.txt | xargs -d "\n" sh -c 'for args do echo =--= $args =--=; sqlite3 -column -header -csv -cmd "select * from images where id=${args};foobaz" -bail meta.sqlite 2>/dev/null; done' _
>[...]
>id,md5sum,type,uploader,tags,source,rating,date,origfn,w,h,size,filename,sel
>198564,660245ba3fe21842eb78ea32daf438de,png,Anonymous,dolan_is_best_pony,,safe,"2012-06-14 23:13:07.008639",tumblr_m5llx7zvYF1ryv213o1_500.png,500,562,179059,"198564 - dolan_is_best_pony.png",

Three-test: 195484.html + 59794.html + 18353.html from 2012-10-18 and 2012-07-28 =
>No image in the database has the ID #195484
>No image in the database has the ID #59794
>No image in the database has the ID #18353

Almost no way to know what the remaining 8367 deleted images were. Maybe some of them (or their webpages/thumbnails/whatever) were saved to WBM. Here's "poni_del.txt":
https://ipfs.apillon.io/ipfs/QmaYHogHfkJxMcmPxK1FgfaviqE7rBWyRB4bSzAgkjtf9E