import maya.cmds as cmds
import os
from os import listdir

def UI(*args):

    if cmds.window("Test", exists = True):
        cmds.deleteUI("Test")
    mainwindow = cmds.window("Test", t="Test Window", sizeable = 1)

    cmds.scrollLayout('srcoll', p = "Test")
    cmds.rowColumnLayout("ColLayout", p = "Test", nc = 3)#I imagine the "nc" command is probably useless here, I am just leaving it for testing purposes

    cmds.showWindow("Test")

customPath = "C:Users$username$Desktop"
customPathItems = listdir(customPath)


def popUI(*args):
for item in customPathItems:
    if item.endswith("_icon.png"):
        cmds.iconTextButton(l = item, p = "ColLayout", i = customPath + "/" + item, w = 128, h = 128)


def buildUI(*args):
    UI()
    popUI()

buildUI()