@Caymon: The GIMP have a pen-drawed filter (Filter -> Artistic). When set on radius 5 and black percent 0,1, it gives something like this:
The changes are minimal but it should stick better with other icons. What do you think about it?
EDIT: Added a small police icon tryout.



The changes are minimal but it should stick better with other icons. What do you think about it?
EDIT: Added a small police icon tryout.