I did a piece for grade 6 (many years ago - can't play it any more) that had loads of double and triple stopping which sounded quite cool when I got it right (ie very rarely)
Just looked it up - Wienawski Chanson Polonaise, Op12 no. 2
Was on the 95/96 syllabus lol
The RVW Greensleeves Fantasia's about G6 I think.
How about the Faure Berceuse? Is that also? I had it in a book somewhere

Some of the Shostakovich Albumstucke might be the right kind of level.
& maybe the first and/or last movements of the Dvorak Sonatina? Don't know that they're really G6, but they're fun and quite show offy for their level

My violin rep. knowledge is a bit out of date but hope that helps a bit!