I got this script from yt that is supposed to change the mouse cursor, but it's giving me this error: Image "https://assetdelivery.roblox.com/v1/asset?id=3090499091" failed to load in "Mouse Cursor": Request failed. I don't really know what is the problem, but here is the script:
local mouse = game.Players.LocalPlayer:GetMouse() mouse.Icon = "http://roblox.com/asset?id=3090499091"
Try replacing
mouse.Icon = "http://roblox.com/asset?id=3090499091"
with
mouse.Icon = "rbxassetid://3090499091"
Also make sure this is in a local script. If you just uploaded the image it may take a while for it to be approved which may cause the error. Either that or it's an invalid ID. The code you provided should be working fine.
EDIT: So this is because you're trying to set the mouse icon as a decal. You need to set it as an image. Try uploading the image directly into studio via game explorer >images > right click > add asset. Then right-click the uploaded asset under "images" and copy the ID