Now that Google Image Charts are deprecated and only have a year or two left before they can shut it off. Are there any other options out there for creating image based charts (as opposed to JS-based charts)?
As said in comments, ChartURL is not a real drop-in replacement to Google Image Charts.
However there is actually **Image-Charts a fully compatible replacement for Google Image Charts.
The only required change to VisualForce scripts is to replace
Bonus it even supports animated charts through gif generation: