Fra Lippo Lippi is Browning's poetic representation of a historical figure of the fifteenth century, a monk was noted for his realistic artworks. We expect him to speak of people, places, and events of that time, and the good Bro certainly doesn't disappoint. We get many references to the paintings he completed—among them his masterpiece, which he describes in the last section of the poem: "The Coronation of the Virgin."
Aside from this historical angle, Browning speculates on the type of person Lippo might have been by giving him his own voice. He appears a rather convivial and feisty monk. He's out partying and gets caught by some guardsmen, with whom he shares some banter and for whom he buys rounds (so, basically, he bribes them to leave him alone).
He's also a bit of a rebel. Despite being scolded by the church higher-ups for not attending to the spiritual side of things in his artwork, he professes his own artistic philosophy of painting things that are real. He argues that the best painting takes something familiar and makes the viewer see it in a new way.
Lippo is also a bit naughty. He's out mingling with "sportive women," who we should probably read as "women of the night." He also seems to know what it feels like to frolic around on a woman's "kirtle" (a gown—presumably one that has been removed from the lady in question). He justifies this behavior by saying, "You should not take a fellow eight years old/ and make him swear to never kiss the girls" (224-225). This totes gives us a big clue that he became a monk out of necessity (he was starving to death) and not out of any true spiritual calling.