by Mary Evans.
Hi Nadav,
John's reply is a good way to do this and is less intrusive and easily reversed if someone prefers the original way the block works.
To add the switch_minus.png and switch_plus.png images to your theme you need to create a pix_core/t/ (directory/sub-directory) in your theme folder and then add 2 tranparent images to replace the normal images that are called from moodle/pix/t directory.
Example:
standard/pix_core/t/
standard/pix_core/t/switch_plus.png
standard/pix_core/t/switch_minus.png
Shalom
Mary