As others have pointed out, that's called a light box, not a carousel. And while light boxes are not in principle bad UI, they are often poorly implemented. On

As others have pointed out, that's called a light box, not a carousel. And while light boxes are not in principle bad UI, they are often poorly implemented. On many pages, clicking a thumbnail opens a light box that adds so much margin "for design considerations" that the image ends up actually shrinking. Drives me nuts every time. I think twitter recently fixed this. Only took them a few years to notice, yay!