I would usually have a random (constrained) fixation screen duration between stimuli (ISI).
In OpenSesame this works (e.g. for fixation duration approx 1000ms, varied between 750 and 1250ms):
var.fix_duration = random.randint(750, 1250)
Does anyone have examples of how to convert this to OSWeb Inline in order to use it in an online experiment?