Why keep images in tiles graphic array?

By this time, there are duplicated tiles, one as an image and one as graphic:
``` javascript
const initialTileCount = tiles.length;
for (let i = 0; i < initialTileCount; i++) {
let tempTiles = [];
for (let j = 0; j < 4; j++) {
tempTiles.push(tiles[i].rotate(j));
}
tempTiles = removeDuplicatedTiles(tempTiles);
tiles = tiles.concat(tempTiles);
}
console.log(tiles.length);
```
Example: