Module:Carousel

p = {}

-- carousel returns one of a list of image filenames
-- the index of the one chosen increments every 'switchsecs'
-- which is a parameter giving the number of seconds between switches
-- 3600 would switch every hour
-- 43200 would be every 12 hours
-- 86400 would be daily (the default)
-- {{#invoke:carousel | nain | switchsecs = number-of-seconds }}
-- {{#invoke:carousel | main }} for 12 hours between switches
p.main = function(frame)
	local switchtime = tonumber(frame.args.switchsecs) or 86400
	if switchtime < 1 then switchtime = 86400 end
	local imgs = {
		"Pelicans 11.3.2007.jpg",
        "Little Chief Mountain.jpg",
		"Great Blue Heron and immature Bald Eagle on the Platte River.jpg",
		"Green Heron4.jpg",
		"Canada Goose mating ritual2.jpg",
		"North Swiftcurrent Glacier (2).jpg", 
		"Adhela and Guy Fawkes 1873.jpg",
		"Flock of Cedar Waxwings3.jpg",
		"Fusillade Peak 2.jpg",
		"Lightning 7.11.2008.jpg",
		"Ursus americanus.jpg",
		"Jackson Glacier 7.2017.jpg",
		"Stone Creek Nebraska.jpg",
		"Grus canadensis2.jpg",
		"Scaphirhynchus platorynchus 6.14.2014a.jpg",
		"Painted Tepee.jpg",
		"Bison Bull in Nebraska.jpg",
		"Horses and thunderstorm1.jpg",
		"Going to the Sun Falls.jpg",
		"Lillypads at Desoto.jpg",
		"Steamboat Geyser.jpg",
		"Fusillade Mountain.jpg",
		"Lake view from Beartooth Pass.jpg",
		"Tetons from Togwotee Pass.jpg",
		"Inspiration Point.jpg",
		"Flowers b grow to 6 feet.jpg",
		"Storm Front2.jpg",
		"Bird Woman Falls 2017.jpg"
	}
	local numimgs = #imgs
	local now = math.floor( os.time() / switchtime )
	local idx = now % numimgs + 1
	return imgs[idx]
end

return p
Usage
