Help!

--[[Ok so we're going to use HttpService to check if said string is an id.
we're going to use rproxy's getidbyusername API that returns -1 if nonexistant. So make sure httpservice is enabled.]]

local prox = game.HttpService:GetAsync("http://www.rproxy.tk/rapi/GetIdByUsername/SethDusek5
function check(stringy)
local prox = game.HttpService:GetAsync("http://www.rproxy.tk/rapi/GetIdByUsername/"..stringy)
if prox == -1 then return nil
else return prox
end

Soo, now you want to know how to use an image of that person
local decal = Instance.new("Decal",workspace.Part)
local checker = check(name)
if checker~=nil then
decal.Texture = "http://www.roblox.com/Thumbs/Avatar.ashx?x=100&y=100&userid="..checker
end