I'm really not sure what level grade 7/8 is in your terms, I know only the Australian version, AMEB.I'm also not sure what you would like exactly, I guess I can only suggest pieces in line with my own taste...But anyway, here are some approximately appropriate pieces.I would recommend some Chopin Etudes that are easier like Op. 10 no 3, 6 and also the 3 etudes tacked on, which are mostly studies in polyrhythms but are quite lovely in their own way.Speaking of Chopin, look at his Waltzes and Mazurkas. Also Preludes Opus 28 No 3, 21 and Opus 45 in C sharp minor.Check out Tchaikovsky's "The Seasons" like January and June.Also Maybe a Scarlatti sonata, maybe K 96?And maybe some Preludes and Fugues from the Well Tempered Klavier... like C minor and D minor in book 1 and F minor in book 2.Anyway, I hope that gives you some ideas
love this, Rachmaninoff-Gryaznoff :scorehttps://www.schott-music.com/shop/1/show,320769.html
For something different you might want to pick a piece from Moskowski's Op. 91 - a whole bunch of short etudes around grade 7-8 in that.Also, try checking www.pianosyllabus.com - enter etude into the title field and 7 into the grade field and you'll get quite a few hits. Same with nocturnes and grade 8.