heres some css codes because im feeling generous lmao, and css is hard
body{
background-attachment:fixed;
background-image:url(insert gif here );
background-position:center;
background-size:cover;}

body{
background-attachment:fixed;
background-image:url(insert gif here );
background-position:center;
background-size:cover;}

(side note: i got this one above from someone else and it didnt work for me, if it works for u thats cool :D)

body{color: type in a color here;}

body{background-image: url(put image url here)}

also, to put an image/gif in your about me like how i did with the sebastian and pefect blue ones is just go google an image and copy the images url, then paste the url in the about me, no coding needed, hope this all helps
enjoy :)

https://youtu.be/xWUNXPa96R0