I tested it with JS enabled and you are right. It seems IMDb has changed their JS and it interferes with the addon function (if JS is enabled on IMDB). I will find a fix and post an update.
Thank you for letting me know.
Update: I found that "Remove LoadLate" clashes with IMDb script, if JS is enabled. if you disable the "Remove LoadLate", the "Bigger Thumbnails" should work.
I am still working on it.
Update 2: I have fixed the problem (I hope) and I am testing. I will upload an upgrade soon.