We had nice cotton PJs in EK F on a recent JFK-DXB flight. They were a different style than previous ones -- just a slip on shirt with an Emirates crest near the hemline of the shirt. Nothing on the pants. Very comfortable, and the FA offered to let me keep them, so I did. (One of the best FAs ever, on any airline, btw).
We also got plain brown hotel-like slippers with a discrete "Emirates" tag.

EDITED: On inspection the PJs were actually a cotton / polyester blend ! But fairly comfortable nonetheless.