Minimizing image size of small images (16x12px)

[Woppe]

Hi!
I got thousands of small thumbnails, 16x12px, which I have to make as small as possible.
Right now I save them as jpeg's with a compression quality of 70. That makes them end up at around 370 byte each.
Is there any way to make them smaller without loosing too much quality?

Thanks in advance!