What is this? Serve a fake known ad (url owned by you) and see if its get loaded or not? i.e.: if a client doesn't load it, then it has an ad blocker installed?
For example, instead of the tracking.usermaven.com URL in the pixel, you'll be able to use tracking.yourdomain.com so that adblcokers would see it is a first-party tracking URL and won't block it.