Let me install my version of PDeR (1.0a) and see what's happening there.
export_unit
Code:
{Iberian_Cavalry}Caballeros Hidalgos
EDU
Code:
type Iberian Cavalry
dictionary Iberian_Cavalry ; Iberian Cavalry
category cavalry
class light
voice_type Light
banner faction main_cavalry
banner holy crusade_cavalry
soldier Border_Horse, 24, 0, 1
modelDB
Code:
12 border_horse
1 4
59 unit_models/_Units/EN_Peasant_Padded/border_horse_lod0.mesh 121
59 unit_models/_Units/EN_Peasant_Padded/border_horse_lod1.mesh 900
59 unit_models/_Units/EN_Peasant_Padded/border_horse_lod2.mesh 2500
59 unit_models/_Units/EN_Peasant_Padded/border_horse_lod3.mesh 6400
No border_horse model (mesh) in the folder!
There are however 4 models of 'iberian_cavalry' in that folder which I guess were the models supposed to be used.
Find attached the corrected modelDB file and extract it into the data\unit_models folder. Please report back if that solved the problem and if the textures are displayed correctly.