Does anyone have any suggestions of any piano duets for level 6?

Is that grade 6? What sort of music are you interested in? Classical, Jazzy etc...?

I am looking for something either in the Classical period or Romantic.

Have you thought of the Moszkowski Spanish dances or Grieg's Norwegain Dances? Both for 4 hands/1
piano and great fun. Also Arrival of the Queen of Sheba (Handel)

I did Grade 5 as a piano duet exam many years ago and played a Clementi Rondo and a Brahms Waltz. At about the same time we also played the Spanish dances Fionamck mentions and these were great fun (more so than the Clementi and the Brahms).