You can customize your album's looks either by clicking an edit icon on the page with the list of all albums, or the link Edit Album Settings on the page listing an album's photos, in the left bottom corner.

Here you can change an album's name and description, choose its skin and set thumbnail parameters, such as size and number on the page.

Note: the skin you have chosen on this page will not be applied to the page with all your albums. You can choose a cover for the latter on the Account Settings page. You will move on it clicking My Account tab.