W3 Total Cache and resized thumbnails

Hi,
im using the UPW to display latest posts and showing thumbnails…
i have installed the W3 Total Cache plugin on the site, and it doesn’t seem to help reducing the amount of processing needed to get the images
since every image is requested from a php file (/thumb.php?src – TimThumb)

the images gets this link, which is not cachable
http://www.my-site.com/wp-content/plugins/ultimate-posts-widget/thumb.php?src=http://www.my-site.com/wp-content/uploads/2013/12/s1012201301s.jpg&h=100&w=100&zc=1

is there any way that we can make WPU work with caching? maybe im missing something, any help would be appreciated!

maybe i can resize the images beforehand, and make UPW severe those images instead of using TimThumb? can that be done?

http://ww.wp.xz.cn/plugins/ultimate-posts-widget/