DSF

Ive used various types of Hydroprint film.....white and clear permanent or "cling" successfully on stuff like this.....look at the various recommendations on them re light, temperature etc. I print them on my Xerox 7500 then overlay them on to my project. If I have a specific shaped project, I print then cut on the cutter, then overlay on the final product. Hope this helps

I was thinking a film might be better and work, maybe printed onto a metal plaque, lined with film then screwed onto a wooden board

If the wood had a smooth enough finish, I don't think you'd need the metal, unless, of course, you wanted it as part of the design. The stuff I've used is called Hydro Print from Kernow Coatings Limited, they have a web site but don't sell direct but there is a company who does, just can't remember the name of them at this minute