Create a looping bg on the say screen
# Create the Image ATL
image loop_bg:
"bg one"
time 1.0
"bg two"
time 1.0
repeat
# Add it as a background on screen window
# If you are using the default screen.rpy, there's probably a style
# for the window with a bg already defined, you can change it there
screen say(who, what):
window:
background: loop_bg