Hi @matthewj
You can use javascript to make the image URL unique all the time thought adding a “number” (in this case just a simple timecode). :)
OBS: I had to add spaces after the " < " before the end " > ".
Just remove them when you use it. :)
Otherwise it would not show.
< img id="graph" alt="" src="https://plot.ly/~myPlotlyAccount/myGraph.png" />
< script language="javascript" type="text/javascript" >
var d = new Date();
document.getElementById("graph").src = "https://plot.ly/~myPlotlyAccount/myGraph.png=" + d.getTime();
< /script >
Good luck. :)