I'm unclear on what the requirements are for the custom images. How big should they be? Where should they be uploaded? What format? Apologies if I missed all of this in the instructions. I didn't see any discussion of these things.
And what happens if you don't use custom images? Does the add-on fail?
This resource has been removed and is no longer available for download.
These original free ones contained links back to the original owner's site (who is no longer involved with them), and the resource page indicated they'd eventually be deleted.Why has this been removed and what does it mean "obsolete"?
We use this very successfully since several years and it is the most successful captcha you can get for XenForo. No more spam contact mails!