"Pictor Ignotus" sets its Italian Renaissance scene through allusions to the triumphs and struggles of the 16th-century art world.
One of the most prominent of those allusions touches on the "youth" whom, as the speaker enviously (and endlessly) repeats, everyone "praise[s] so" these days. Odds are good that this brilliant youth is Raphael. Raphael was a Renaissance wunderkind, a genius who flashed like a comet, then died young. His tender, naturalistic paintings changed the course of visual art.
The speaker's vision of the pictures he could have painted, with "each face obedient to its passion's law," suggest what was new and astonishing about Raphael's art in particular and Italian Renaissance art in general. The big innovation in Renaissance art was a new humanism, an interest in capturing distinctive faces, fleshly bodies, and believable emotion—as contrasted with the stylized, flat, symbolic conventions of the medieval period.
No wonder, then, that this speaker feels particularly envious of the brilliant youth. He himself seems to be a more old-fashioned painter. His endless devotional paintings of "Virgin, Babe and Saint" suggest that he's almost a pre-Renaissance man: those identical faces, all wearing the "same cold calm beautiful" expressions, sound closer to medieval iconography than lively 16th-century humanism.
Behind the times artistically (and all too well aware of it), the speaker must also grapple with a characteristic Renaissance attitude toward art. While contemporary readers might be inclined to think of Renaissance painting as lofty and sublime, it was made in a decidedly earthy context. Renaissance Italy was a place marked as much by money-grubbing and power plays as a flowering of the arts, and the speaker's portrait of the shallow, nattering merchants he wouldn't have wanted to sell his art to anyway picks up on an ironic truth about the era. The Renaissance didn't just birth immortal works of art, it commodified them and treated them as status symbols. (Browning reflected on that irony more than once in his dramatic monologues.)
On the other hand, the Renaissance world truly revered art and artists. When the speaker describes his lost dream that his paintings might travel to their new homes like heroes, with "flowers cast" in the path of the carts carrying them and "old streets named afresh" to celebrate their arrival, he's drawing on a true story. In his Lives of the Artists, the Renaissance art historian Giorgio Vasari includes a tale in which a painting of Cimabue's (a great master of the early Renaissance) was celebrated in just such a fashion.
The speaker's most poignant forlorn hope, though, is that he might achieve a kind of immortality through his work. Browning makes this point through a funny little anachronistic allusion. When the speaker imagines that part of him could have lived on in his paintings after his death, he wistfully says that "earth's every man" would have been his "friend"—language that echoes the English Romantic poet Keats's "Ode on a Grecian Urn." In that poem, which likewise reflects on art's immortal power, Keats calls a beautiful ancient Greek urn a "friend to man." Perhaps this subtle reference does Keats himself (a favorite of Browning's, and like Raphael a brilliant, short-lived "youth") some honor.