Well interestingly enough, in the Three.js WebGL framework, I haven't found a way to draw directly to the screen. Apparently you must add objects to the screen. Like with sprites. And it draws super fast.
As long as you keep those objects organized you should be fine.
Here's pseudo Three.js code:
var level1Tiles = new Group();
for (x = 0; x < width; x++) {
for (y = 0; y < height; y++) {
level1Tiles.add(new Sprite(groundTexture, x, y));
}
}
scene.addObjects(level1Tiles);
scene.removeObjects(level1Tiles);
That's how Three.js is set up and it's blazing fast.