Welcome.
You can try the new standard-template with jpgimgthumbs and picturviewer
addon.
This addon downloads only the first 64kB from images and extract the thumbnails.
If this don't work, because you have no thumbs in your jpegs, then try
dnd_upload_thumb.
It generates thumbs on the fly on (dnd) upload. Create subfolder thumb.
You can also use querystringparameter ?onlythumb to create only thumbnails.
update: dnd_upload_advanced with querystringparameter ?auto creates thumbs from all pics (without upload)