Thanks, Bernd. It helps. I had been confused, I have the history of the two back to front. I made the icon for Keith which made me think perhaps it could be good for FEM, but don't worry if it is not needed. Also feel free to contact me and ask if you want something different or something else.
By the way I followed the links in your code and read wikipedia ... wow! Some intellectually intense stuff! My children think it is evidence that you are more intelligent and educated than I, which is true of course, so I went out into the paddock to see Charlie, my smelly pet billy goat, he thinks I am far more intelligent than you because I know where to get his treats like hay, milk thistle, bread and especially half stale chocolate cake and slightly over cooked home made biscuits! So the life lesson is if you want an undeserved complement, just ask someone for their opinion who is in the habit of urinating on his legs in order to make him stink really bad, in an attempt to attract his girl friend!
This is where I got to with a NetGen icon for FreeCAD. I will post it here in case it is ever useful. It is based on their logo, but since its intended as only an icon it is less detailed. It is not perfect but it is where I have go to so far.
At 64px at 32 px
and at the most commonly used resolution/size, 22 px
If we had a fixed number of options like different mesh generators for example, in other areas of FreeCAD we have an icon on the tool bar with a drop down, the default is shown only before the drop is activated then which ever was last used stays on top.
For example have a look at
1) PartDesign additive or subtractive solids,
2) sketcher insert a circle from either Centre and point or 3 points on circumference
3) Sketch Radius constraint or Diameter Constraint
But as you say, there could; be other ways more useful to the specific workflow requirements of FEM.