A fast image viewer that has helped me when cleaning up images.
Click the open folder icon, select the first image and then use these keys:
LEFT/RIGHT view previous/next image
BACKSPACE/DELETE delete* current then move to previous/next image
Keys A...Z will move the image you are viewing under subfolder _A..._Z
Ctrl-Z undos the last deletion or move to subfolder
*: In fact images are never deleted but are just moved to subfolder _deleted