I am guessing this is partially driven by an aesthetic concern?
Plastic trunking isn't used for safety, it is used for cable management and routing. Where there is a safety concern (ie buried cables in non-safe zones) then earthed metal trunking is required.
There is nothing wrong with using other types of trunking & you can already acquired wood/wood-effect trunking.
Just be aware, if such "trunking" is outside of the safe zone it is not so inconspicuous that others may not consider there any cables. Has the end effect resulted in essentially a buried cable consideration simply because of the nature of how you concealed the cables.
Cables in a wall or partition
A cable concealed in a wall or partition must be at least 50mm from the surface [If the wall or partition is made from or partially made from metal then the cable will require RCD protection or be installed as 2), 3) or 4) below]
have earthed armouring or an earthed metal sheath (eg SWA, a BS 8436 cable or MICC cable)
- be enclosed in earthed steel conduit or trunking
- be provided with mechanical protection (3mm steel is deemed sufficient to meet this requirement)
The safe zones for cables concealed in walls are
- a horizontal zone within 150mm of the top of a wall
- a vertical zone within 150mm of the angle formed by two walls - e.g. internal and external corners.
- the horizontal and vertical zone adjacent to an electrical accessory (switch, socket, cable outlet etc)