The troop labels floating over the heads of individual soldiers are images taken from the centre of each army/party flag, using Warband’s heraldic system. To change the images you need to edit the dds banners files in an image editor such as gimp or photoshop. If you also want to change the mesh floating over soldiers heads to remove the circular ring & just leave its alpha transparancy, you need to edit the troop label mesh in user_interface_b.brf using OpenBRF.