how do i get an image to change on refresh?

[Birdy]

i'm so sorry if this is not the place to ask this ;u;

i remember a long while ago, it was a thing where users could change which pets showed up in their signature each time the page was refreshed, but i can't remember for the life of me how to do it lol. any help is appreciated!

[Burrito Bunny]

These images can be made using this website! http://sig.grumpybumpers.com/

[Birdy]

These images can be made using this website! http://sig.grumpybumpers.com/

yayyyy thank you so much!! <3