Generate up to 4000 pngs with random names could be a tedious task without a script... But easier with this little piece of code using Node.js, async and Fabric.js:

var fs = require("fs"),
  fabric = require("fabric").fabric,
  async = require("async");

var names = ["Coleman", "Simon", "..."];

async.eachSeries(
  names,
  function(name, callback) {
    var path = __dirname + "/images/" + name.toLowerCase() + ".png";
    var out = fs.createWriteStream(path);

    var canvas = fabric.createCanvasForNode(300, 200);

    var text = new fabric.Text(name, {
      fontFamily: "Christopherhand",
      fontSize: 60,
      fill: "#FF0000",
      left: 0,
      top: 0
    });

    canvas.add(text);

    var stream = canvas.createPNGStream();
    stream.on("data", function(chunk) {
      out.write(chunk);
    });

    stream.on("end", function() {
      callback();
    });
  },
  function(err) {
    console.log("done!");
  }
);