I recommend some of the solos in the Julie Davila book, Impressions, the "Lute and Guitar" book edited by Rebecca Kite. You can also look at Strive to be Happy by Ivan Trevino and Ghost Garden by Adam Hopper.
Check out the shorter 2-mallet pieces by Koshinski as well.
: Any suggestions for easy class 1 marimba
: 4 mallet & 2 mallet