1) speed - XYPlorer makes it a bit slow. XY made 235 HQ 256x256 thumbnails in about 5 minutes, while imagemagick\convert.exe -thumbnail 256x256 *.jpg did job in 10 seconds.
2) custom thumbnails - for e.g. movies in containers where you can't put cover art (like .avi)
3) thumbnails for unsupported file types - in my case they are SVG and PDF
Also I bet I could reverse engineer thumbnail database. Would be it ok for you, mr. author (sorry, next time I'll find your name
* if you need something, I'll draw it for you. I mean as a help, as your tool helps me, not as asking for job
XYplorer Beta Club