I've just designed a PNG for the workspace margins dialog which might look better than the current one.
It's based on an icon of the tango icon theme, I removed some elements of the icon and added the dotted margins. Please consider it to replace the current image.
Created attachment 2009
Can you also provide the SVG version that was used to create the png along with the credits?
I try now to include the svg source so someone can modify the icon later if needed.
Created attachment 2016
new version based on new svg file to be attached in a second
Created attachment 2017
svg file for the icon
Committed with some modifications, rev. 28983.
Thank you ! And sorry for the licensing trouble...