Sumptuous rhymes with:
impetuous, incestuous, unctuous, assiduous, fatuous, impetuous, incestuous, inconspicuous, marquess, presumptuous, promiscuous, sensuous, sinuous, tenuous, tortuous, unambiguous, unctuous, voluptuous
Sumptuous sounds like:
snippets, somebody's, symbiotic, sympathetic, sympathies, sympathize, sympathizes, synbiotics, synoptic, synoptics