In the 1920's and 30's jug band styles ranged from country blues to dixieland. In those days, by definition, a jug band had a jug player, sometimes more than one. Some of them were pretty damn good, taking it way beyond the novelty level.

In the 60's the definition was broadened by Jim Kweskin's band and others. Kweskin included 20's pop songs, blues, folk, old-time country and even rock'n'roll. Sometimes they used a jug and sometimes they didn't. That has been the model ever since.

I love jug band music and my only complaint with contemporary jug bands is they stick to closely to material recorded by Kweskin. There are dozens of real jug band songs yet to be covered and an infinite number of other songs that would sound good played by a jug band.

I don't know of any contemporary Christian jug bands but I have a compilation CD called "The Jug & Washboard Bands- vol 2 (1928-1930)" which includes two cuts by Rev. E. S. "Shy" Moore. Each is a hellfire sermon followed by a spiritual accompanied by a jug band.