check comments

right click on any image and click inspect and find something that looks like this

right click and do "edit as HTML"

go to the image you want to replace it with and do the same, except do ctrl+a+ctrl+c on the img id thing for the image you want to replace the original one with

after that just replace the entire thing with the other thing

erase this and replace it with the other one

now it loads as this even though the URL is https://imgflip.com/i/8qpg5y

which redirects to an image that looks like this