Currently, players are identified by their names in the UI. This applies to several places (OR company ownership, portfolio overview, various popus).
In addition to that, the names should be accompanied by player portraits. They could be displayed in different sizes (larget portrait for popus, small ones for portfolio/OR overview).
There should be default portraits available (some robber barons as for SimTex's 1830). Still, the player should be able to use specific his own portrait.