maybe one small way to differentiate between old time and bluegrass is that so many old time musician artists are really great artists while bluegrass art as a genre tends toward the style modulating between kitsch and socialist realism.
here is an example
Actually, I have to say that I love this one of Bill Monroe playing in the sunny glade on his way to the Gloryland. Heartbreaking, no?
These paintings definitely share a sensibility with the neo-Confederate art of that dude Mort Kuntsler
(yes I did misspell his name deliberately, to amuse myself. It isn't hard).