I am a cellist primarily, but am looking to improve my piano skills. I can play the first prelude by Bach from the Well-Tempered Klavier, and also can play the Solfeggieto by CPE Bach. Any ideas on other music from the piano repertoire that would suit me well?

As a start, explore pieces set for Grades 4 and 5 in the ABRSM and TG syllabi.

Beethoven - Bagatelle in G minor op.119 no.1
Debussy - Le Petie Negre
Clementi - op.36 Sonatinas
Bach - little Preludes, Two parts inventions
Khachaturian - Pictures form Childhood suite (one of my favourites!)
Shostakovich - Dances of Dolls suite

... there are lots more...
Enjoy!
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You could get hold of Classics to Moderns (and More c to m) probably around book 4 or book 5, and explore the contents to give you some more ideas. Most of the pieces are relatively short, but may spark interest in composers you hadn't thought of.

Mozart sonatas?