How to decorate the inside of a metal trunk?

You could line it with wallpaper or paint it with paint made for metal, like Rustoleum. You could even fabric line it if you want.

Most people line it with wallpaper.

Hi Pam, I've seen some pretty ones with old newspaper decoupaged inside. It gives the trunk a vintage look.

You could decoupage the inside with book pages, wrapping paper, scrapbook papers, sheet music, dictionary pages, etc. You could even decoupage fabric too!

Hi! I used decoupage to decorate the outside of a trunk but you could also do the same with newspaper or wallpaper on the inside >> https://www.homeroad.net/2014/05/vintage-book-page-trunk.html