I've just decided to give this a whirl (my first time) and figured I'd give some feedback.
- The text is a little hard to read. It's sort of... gravelly. And the lower case a isn't very clear at all. I really can't say I like the font I'm afraid.
- The icon for railway building in the tool-bar is very dark, I wouldn't know it was railways if I didn't already know (if that makes sense
).
- The "list company trains" train icon in the toolbar doesn't look like a train to me. It could just be another road vehicle.
- The little blue dots (or stars or whatever they are) on the zoom in/out icons don't add anything and make the - and + parts (especially the +) harder to differentiate.
- The airport building icon on the taskbar seems a little out of place when compared to the three icons to its left for the other industries.
- The landscape icon the green seems a bit too dark, it's hard to tell what the icon is showing.
Apart from those things, it's a lovely set and great work, My biggest issue is with the text, it's just so hard for me to read (and I don't have anything wrong with my eyes that I know of), it's really something of a show-stopper.
Keep up the good work though!
as it's quite time consuming to maintain all those different pieces. But yes, I was referring to those single grfs. Sure enough I got the latest OpenGFX via bananas 
) which one likes 
... 
...
: