Batch importing, texturing, and rendering via Python

Here is an example. Edit the variables at the top to configure it, then run.

The renders will be placed next to the .gltf files (eg. Some_Mesh_render.png).

import bpy
import os


######## Edit these ##########

# Full path to the directory containing Meshes/Textures folders
root_dir = "/path/to/your/dir"

# Name of the master material
master_material_name = "Master Material"

# Name of the Image Texture node for the diffuse texture
diffuse_node_name = "Diffuse"

# Name of the Image Texture node for the specular texture
specular_node_name = "Specular"

# Name of the Image Texture node for the normal texture
normal_node_name = "Normal"

##############################


def do_gltf(gltf_path, render_path, diffuse_path, specular_path, normal_path):
    bpy.ops.import_scene.gltf(filepath=gltf_path)

    for ob in bpy.context.selected_objects:
        if ob.type == 'MESH':
            mat = bpy.data.materials[master_material_name].copy()

            # Place copy of master material in first material slot
            if ob.data.materials:
                ob.data.materials[0] = mat
            else:
                ob.data.materials.append(mat)

            # Swap in textures
            dif_img = bpy.data.images.load(diffuse_path)
            spe_img = bpy.data.images.load(specular_path)
            nor_img = bpy.data.images.load(normal_path)
            mat.node_tree.nodes[diffuse_node_name].image = dif_img
            mat.node_tree.nodes[specular_node_name].image = spe_img
            mat.node_tree.nodes[normal_node_name].image = nor_img

            # Render
            bpy.context.scene.render.filepath = render_path
            bpy.ops.render.render(write_still=1)

            break

    # Remove imported objects when done
    bpy.ops.object.delete()


mesh_dir = os.path.join(root_dir, "Meshes")
texture_dir = os.path.join(root_dir, "Textures")

for folder in os.listdir(mesh_dir):
    mesh_group_dir = os.path.join(mesh_dir, folder)
    texture_group_dir = os.path.join(texture_dir, folder)

    for f in os.listdir(mesh_group_dir):
        if not f.lower().endswith(".gltf") and not f.lower().endswith(".glb"):
            continue

        name = os.path.splitext(f)[0]
        do_gltf(
            gltf_path=     os.path.join(mesh_group_dir, f),
            render_path=   os.path.join(mesh_group_dir, f"{name}_render"),
            diffuse_path=  os.path.join(texture_group_dir, f"{name}_diffuse.png"),
            specular_path= os.path.join(texture_group_dir, f"{name}_specular.png"),
            normal_path=   os.path.join(texture_group_dir, f"{name}_normal.png"),
        )