Depending on colour & mortar gaps...
- Nylon P-clips into small rawlplug & screw (can look ok a-la-pyro)
- Fischer or similar "U"cable clips (drill hole, loop over cable, push-
in)

Whatever, try to avoid festooning which can look ugly.

Nail-in clips can compress aerial cables when used ham-fistedly.
If you go that route, instead of wooden dowel perhaps rawl-plug pieces?