Thumbnail cache does not clean thumbs.db, and it is not supposed to
[Thumbnail Cache]
ID=1029
LangSecRef=3002
LangRef=3131
DetectOS=6.0
Default=true
SpecialKey1=N_EX_THUMBNAIL_CACHE
FileKey1=%LocalAppData%\Microsoft\Windows\Explorer|thumbcache_*.db
FileKey2=%LocalAppData%\Microsoft\Windows\Explorer\ThumbCacheToDelete|thm*.tmp
unless Special key is that, but I don't believe it is