Is it just the little picture? I had that too, it turns out two files names got mixed up, you need to go to EB\Data\UI\UNITS\PARTHIA and find #steppe_cavalry_parthian_general.tga and rename it #steppe_cavalry_grivpanvar.tga.

Don't think you need to keep the old #steppe_cavalry_grivpanvar.tga so you can just delete it or rename it #steppe_cavalry_parthian_general.tga