In order to browse all available skins you have to click the Browse All button located in the top-left corner of the gallery window. If you hover your mouse over a skin thumbnail, the full-size preview will be displayed.
However, because there are so many skins, gallery provides an option to search skins by tags.
Tag is a keyword or a phrase that functions as a category label. For example: "light blue" yellow simple, describes skins that contain both light blue and yellow colors and can be considered simple in their design.
In order to perform a search, type some tags into the search box located in the top-right corner of the gallery window and click the Search button. After a while list of available skins matching your query will be displayed.
Please, note that you can use buttons at the bottom of the gallery window to browse through search results.