The Bootstrap framework has some modal classes that can be used to piece together a modal image gallery, similar to the 'Reveal Gallery' in Foundation. To see this gallery in action you need to download it. On this page it is just an image.
The images don't have to have the same size or shape, but it certainly looks better if they are the same. If they are a mix of different widths and heights, the dimensions can be set separately for each image.
Hot tip: if you point the left arrow of the first image to the last image, and vice versa, you will get the images in a loop.