I agree, if you want just 1 random image shown per day, then have a column that just says =rand(a1,a2,a3)
and it should randomize those images. The issue with this is that every time the page is updated the image will change. So it wont be a daily change. The way to fix that would be to have a cell populate the current date using the now() function and whenever the page is updated it checks to see if the date matches, if it doesnt it will randomize otherwise do nothing so lets say the random cell is a4, and cell a5 has todays date in it it would look something like this:
a4 would be =IF(A4=A5,"",NOW())
And the cell that is randomizing would be: IF($A$4=$A$5,"",RAND(A1,A2,A3))
It would look something like that, and once you had the first formula made you could copy and past down the line just make sure you keep the $ so the cells don’t change when you copy and paste.