@animage,
You can position image on top of chart as shown in this tutorial or with few lines of code, you can draw it on chart and export as shown in this example.
From what we have observed, sometimes things get delayed mostly when we are not able to reproduce your use-case or not able to understand the exact requirements. Having a JSFiddle helps us in understanding your case better and many a times we can just edit your code on JSFiddle to fix the issue right-away. I request you to brief more along with JSFiddle with your use-case if you have further queries or facing any issue.
—
Vishwas R
Team CanvasJS