How do I make an image cover the entire screen?

I made a pixel grid in medibang to overlay on the screen of the player to create a mosaic effect but whenever I insert the image into the explorer it automatically deletes itself

So Basically you need to put a pcall function into replicated storage and clone that into startergui, like this:

Local pcall = game.ReplicatedStorage.LocalScript

local character = player.nil
local Player = game.Nil.Player.StarterCharacter

if tweened then
game.StarterGui.nil.ScreenGui.Image.Size = nil
and
game.StarterGui.ScreenGui.Size = (1,0,1,36)
game.StarterGui.ScreenGui.Position = (0,0,0,-36)
game.nil.Value.Print("Hello World") -- this will appear in the output to ensure the  script is functioning
elseif game.ReplicatedStorage.LocalSCript:Clone()
function(CloneService).net

wait(9)
print("You're welcome")

Then simply transfer the motor6ds and replicate them into players, and use the oc3 optical line in order to re-clone the following variables.