I agree in some way to let some more symbols into the game. When playing a game like Civ V, you have symbols all over the place, and it can sometimes be a little difficult to remember what each symbols mean. It is, however, extremely consistent so you know that things are the same if it has the same symbol, and you can hover over most of them to get a tooltip. Once you get used to the symbols it is extremely effective, and really makes the information more easily available.
In Simutrans, there currently is a symbol for each waytype, the three major good categories, and a happy face and a sad face if I havent forgotten anything. Already those are not used consistently, for instance the waytype symbols I think could be used in the stop detail window to help differentiate what waytype the different lines has serving the stop, the cargo manifest of the convoy window could display the cargo symbols, together with, or instead of, the cargo category name, just to name a few.
I have tried when I have made GUI-patches to use the existing symbols more, namely the cargo symbols, since those are already very well established in the game. I have used them where it would be too long to write out the good, for instance in the depot window just under the "change prices" button.
What Im worried about is that new symbols doesnt have a meaning yet, for instance the signal symbol you made is very nice I think. It is, however just not established that that symbol would mean "working method". You would need to present that symbol also in the signal info window, and if possible at all also in the tooltip for the signal icon. Otherwise people will not see that symbol enough to connect it with "working method". I would also move the symbol to right before the working method name:
"Current working method: [symbol] one train staff
That way, it would be consistent if you put it into the signal info window right before the working method entry there.
I think the smiley faces in the stop window are nice too, they help draw attention to those numbers which, at least I, often tend to forget all about. The same issue here though:
With this emphasize on the smileys, you need to know what those are all about, and that would be great with a tooltip when hovering above the individual smileys.
I would then go out and find more places those smileys could sit, for instance in the "Stop list", found in the "List's" menu and also in the "line management".
What I would wish for is an icon for each cargo type, wich of corse would be pakset specific. Those icons could live many places, for instance in the convoy window, the depot window, the line window, the individual convoy entries in the line window etc.