Open Ground Manage Picklists

When I access the Manage Picklists in Open Ground and go to StratumDetails-LegendCode. I came across the Values section but unable to edit the image already applied to that value due to it being greyed out. Is there a way to be able to change it so the "Edit Image" isn't greyed out and allow me to access the image that is being applied? Is this something that has been set by our IT person? Also I have read that they are .bmp files but don't know which folder is being used to store the .bmp files. Thus allowing me to change the image to my preference.