Hi Ian,
In my case I created my own HTML with those specific job trends images url:
- YOUR_JENKINS_URL/job/YOUR_JOB/test/trend
I do also use a similar approach with the Plot plugin and the Build trends:
- YOUR_JENKINS_URL/job/YOUR_JOB/plot/getPlot?index=0
- YOUR_JENKINS_URL/job/YOUR_JOB/buildTimeGraph/png
You can resize those images by adding ?width=750&height=450 to the URL
Those urls can easily added as dynamic images to any Wiki system, such as Confluence or any other similar one and it works like a charm
I hope it helps