Random site background by selff is a WordPress plugin that sets a random background on your site from web by season and daytime theme.
Ajax technology. Background loading after the content will be loaded.
Depending on user resolution (window dimension) will be choise the best image link from library; For example: in library store links to images with resolutions: 1600×1200, 1640×1275, 1600×1600, 2272×1704, 3624×2448, 3888×2592. For user with resolution 1368×768 will be choise images with best resolution for this user. For this example is a 3624×2448 and 3888×2592 but ratio of width/height is best for user width reso=1368×768
User may be reload page background with ajax button without reload the page