[UI] Icon for CUSTOM trails

Hello!

Inheriting #19621 .

For custom trails currently there's no icon, as one can see.

and it looks a little bit abnormal, while all other detection types have their own readable icon respectively.

Proposition: While being 100% of user-defined trail(-s) seems good to place some icon like this: https://www.flaticon.com/free-icon/user_9187604 , just to be in the same line of noticing style.