I can’t paste this material through code, but That of using SketchUp paint tool is ok.
use ruby code
face = Sketchup.active_model.selection[0]
material = Sketchup.active_model.materials['image']
face.material = material
# Error: #<ArgumentError: Cannot assign image material to model entities>
# <main>:2:in `material='
# <main>:2:in `<main>'
# SketchUp:in `eval'
# => nil
use paint tool
material = Sketchup.active_model.materials['image']
Sketchup.active_model.materials.current = material
# then use paint tool
test.skp (172.4 KB)