Here are three different layout options for the same gallery (collection of photos). I’ve set them all to display the images at 400 pixels (max height/width) but this can be changed. When you click on any image (in any gallery), it will open a larger version and this will form part of a sequence you can click through to view one at a time.
This is the ‘masonry’ layout. The number of columns can be changed.
This is the ‘mosaic’ horizontal layout. There’s a vertical version too but only one version can be displayed at a time. Also, the overall width of the gallery can be altered (it’s at 90% of the full width of the page at the moment).