Jim, there is nothing whatsoever wrong with that Stan Rogers line, and your objection to it is silly, in my opinion.

Muttley, I think you are mistaken. It was the cowboy who was said to be cold as the clay, not the linen. Who the heck cares whether or not linen is cold? You...or someone else...left out the comma:

"I spied a young cowboy all wrapped in white linen,
All wrapped in white line, as cold as the clay."

And if the dead cowboy spoke...well, hey, it's a song, right? Why can't a corpse speak in a song for purposes of telling a story? A mountain can speak in a song. A tree can speak in a song. Anything can speak in a song.

Where is your sense of imagination, people? Poetry is not to be bound in chains by the banal conventions of the literal mind.