Think it's a useful feature for the next release, so well done on that. 

Cheers, as ever you guys and gals rock!

Adrian

I've added this to the next release.  If you're comfortable modifying PHP code you can try the following changes.  Be sure to create a backup file first.

1. Created a backup of /cmsb/lib/image_functions.php
2. Edit file and search for: save target image
3. Add the code in red:

  // resample image
  $quality = 4; // v2.60 Speed up resizing (was 5 previously)
  _fastimagecopyresampled($targetImage, $sourceImage, 0, 0, $dst_x,  $dst_y,  $targetWidth, $targetHeight, $sourceWidth, $sourceHeight, $imageType, $quality) || die("There was an error resizing the uploaded image!");

  // enable progressive JPEGs
  imageinterlace($targetImage, true);

  // save target image
  $savedFile = false;
  switch($imageType) {

Note that only newly created thumbnails and uploads will be interlaced.  But you can go into the field editor and click "recreate" for pre-existing thumbnails if you want to regenerate them.

Let me know if that works for you!

Standard, but we can add some code to do progressive if you'd like.  Let me know.

Thanks!

Best
Adrian