Showing a clickable image to enter website : how to ?

Dears,

when people type in the url of my site, I would like that the first thing that appear is a clickable picture … and only if they click on this picture, then they are directed to the website.
To explain further, in some way it would be like an advertisement : I have a picture with a Dog and the name of my enterprise, and if people click (anywhere) on this picture the website appear with all the categories etc …
Can someone advice on how to do this ? is there a plugin that enable this feature ?

thanks