Current . . . older US banknotes are the epitome of boring. Newer versions have actual colour, which is good for a plaque, and they usually have a better portrait of the subject on the note. Not a fan of the inkwell, though. Lose that.
Exact copy isn't really an option - the aspect ratio is different on plaques, so it needs to be less wide. Also, I may use a plaque with beveled corners, so there's a different kind of border. But the art would borrow heavily.
Imagine most of the art on the plaque lifted directly off the bill... if it's the modern note, I will probably lose the strip and inkwell entirely, and I don't need the white space for the watermark. I'll let all the elements collapse to the left and have a designer jigger the elements around until they fit well on a plaque. I'd want to keep the color gradient across the bill, and the big ol' Franklin head.
But I'd give the designer a fairly large amount of leeway.