This newer version of Imagus doesn't work at all for me on the Firefox folk I installed it on unfortunately. No image preview was every shown over the images I hover my mouse/cursor on. It's so bad that even the several years-old Imagus extension still does the intended job that this new version was supposed to do.

EDIT: I gave this another try and now the extension is properly working as intended after seeing a new notice from the "options" setting where it reveals that the problem was with the user script not being enabled on default.