I see you used the Diagram Designer. When you set 'Set Group' to 'Automatic' (and press Update!), and then 'Set' to 'Auto Alfaerie PNG' (again Update) the piece overview will also show black, red and green circles. You could use those for Watchers or Peacemaker.
The 'knightguard' symbol there is what is normally used for a piece that moves as a Knight or a King.
BTW, I am able to add other images to this group, so if you have a suggestion for what to use for the neutral pieces, in what color, I could provide it. E.g. non-royal pieces that move as King are usually represented by the 'guard' symbol. So it would make sense to represent the Peacemaker by a differently-colored (grey?) Guard. Similarly, the Watchers could be represented by Queens of that color (as this is how they move). Or they could be a grey circle to resemble the draughts chips that will likely be used in over-the-board play to represent them.
I see you used the Diagram Designer. When you set 'Set Group' to 'Automatic' (and press Update!), and then 'Set' to 'Auto Alfaerie PNG' (again Update) the piece overview will also show black, red and green circles. You could use those for Watchers or Peacemaker.
The 'knightguard' symbol there is what is normally used for a piece that moves as a Knight or a King.
BTW, I am able to add other images to this group, so if you have a suggestion for what to use for the neutral pieces, in what color, I could provide it. E.g. non-royal pieces that move as King are usually represented by the 'guard' symbol. So it would make sense to represent the Peacemaker by a differently-colored (grey?) Guard. Similarly, the Watchers could be represented by Queens of that color (as this is how they move). Or they could be a grey circle to resemble the draughts chips that will likely be used in over-the-board play to represent them.