I have used Hauterive (Ameller) (I believe only available in bass clef),
To a Wild Rose (Macdowell arr. Blaauw), Apres un Reve (is that Ravel?) and Liebesleid (Kreisler arr. Sheridan).
Some of the stuff I've used is not necessarily arranged for Eb Bass or even tuba but for other brass instruments so I've had to be careful as regards register etc.
In Salvation Army repertoire I have used Someone Cares and Prayer of Childhood.
I played an arrangement for tuba and piano of Chopin's Nocturne in E-flat Major, Op. 9, No. 2, for the 2001 NABBA Slow Melody Competition. The range from EEb (pedal Eb) to eb1 (eb above middle C on the piano) fits very well for Eb Bass. The edition is written in bass clef at concert pitch, rather than treble clef.
Danny Boy- I really like that one aswell. I got a copy from Patrick Sheridan's website for Eb Bass and piano. It also has the solo part transposed for you for Bass in C, and Bb- treble clef and Bass clef!