The Roses of Heliogabalus
It's interesting the sort of experience Alma-Tadema's reputation has gone through. During most of his life, he was one of the most highly-paid and highly-regarded artists about. Yet, in the last part of his life, his works became anathema to the art world, to the extent that he was almost completely forgotten after his death, until a recent reevaluation in the 1960's. Though it should also be noted that extremely famous film directors often turned to his depictions for inspiration, despite his then-current unpopularity, such as D.W. Griffith and Cecil B. DeMille. But I can't see much of an argument for unpopularity unless you were to say theme, and that's such a terribly subjective point from which to argue. And one last thing, though I've never read this, I do think that he had a strong influence on the absolutely amazing Maxfield Parrish.
Among the Ruins
A Pyrrhic Dance
A Coign of Vantage
I'd also like to make a quick note about the piece below. While most views of Alma-Tadema were as someone pushing against the various developing movements, notably Post-Impressionism, Fauvism, Futurism and Cubism, he still experimented masterfully with Impressionism, as in the painting Bluebells.