Albert Lavignac, best known for his treatises, composed this Berceuse with clear, transparent textures. It showcases the Romantic penchant for lullaby-like simplicity and sustained cantabile lines.
The main difficulty is executing the cantabile melody with appropriate tonal variety while the left hand provides a constant rhythmic backdrop.
Comparable difficulty and character — good candidates for what to learn next.
Berceuse (Op.18) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Berceuse (Op.18) lasts about 4 minutes.
Berceuse (Op.18) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Am Rhein by Joachim Raff, Barcarolle by Anatoly Lyadov, Barcarolle by Anatoly Liadov — see the full similar-pieces list on this page.