Why won't the decal change, and why am I getting this error?

DISCLAIMER: THIS IS A STORY TO EXPLAIN WHAT MY ISSUE IS AND HOW I GOT TO IT!

I am trying to make a decal changer using a GUI, below represents the code I used.

script.Parent.Submit.MouseButton1Click:connect(function()
    local decalChangerName = "DecalChanger" .. script.Parent.Parent.DecalChangerID.Value

    if string.len(script.Parent.ID.Text) >= 7 then
        if tonumber(script.Parent.ID.Text) then
            game.Workspace.Menu[decalChangerName].Decal.Texture = "http://www.roblox.com/asset/?id=".. script.Parent.ID.Text
            script.Parent.Parent:remove()
        end
    end 
end)

That didn't work so then I removed an if statement and changed 1 line of code. Then I got this.

script.Parent.Submit.MouseButton1Click:connect(function()
    local decalChangerName = "DecalChanger" .. script.Parent.Parent.DecalChangerID.Value

    if string.len(script.Parent.ID.Text) >= 7 then
        game.Workspace.Menu[decalChangerName].Decal.Texture = "http://www.roblox.com/asset/?id=".. tonumber(script.Parent.ID.Text)
        script.Parent.Parent:remove()
    end 
end)

then I get this error inserting my test image

10:18:15.374 - Image failed to load: http://www.roblox.com/asset/?id=10526671: Failed to resolve texture format

Can someone explain how I should change the decal?