You can't enlarge an image. Some skins provide this feature, which is enabled by choosing the album option "Link to originals via scaled images", but I haven't provided this feature in Mirage. In Mirage, all images are reduced to the dimensions that you specify in the "Image bounds" setting.

On a slide page, you can show thumbnails of variants, i.e. other images that are closely matched to the main image. Instructions are in Mirage.pdf, sections 6.2 & 8.4.

However, on a slide page, you cannot show thumbnails of all the other images. If you need this feature, you will have to try a different skin; plenty of good skins provide this feature.

To get comments, you need to configure widgets after you have published the album on the Jalbum site. For more information, refer to the Widgets forum.