かなり手こずったのでメモ
ストレージのファイルを利用してAndEngineのテクスチャとする方法

Sprite base = getBaseActivity().getResourceUtil()
				.getSpriteFromFile(getBaseActivity().getFilesDir() + "/background.png");
		attachChild(base);
public Sprite getSpriteFromFile(String fileName) {
	File imageFile = new File(fileName);
	FileInputStream imageFis = null;
	try {
		imageFis = new FileInputStream(imageFile);
	} catch (FileNotFoundException e) {
		e.printStackTrace();
	}
	Bitmap bm = BitmapFactory.decodeStream(imageFis);
	BitmapTextureAtlas bta = new BitmapTextureAtlas(
			gameActivity.getTextureManager(),
			getTwoPowerSize(bm.getWidth()),
			getTwoPowerSize(bm.getHeight()),
			TextureOptions.BILINEAR_PREMULTIPLYALPHA);
	gameActivity.getEngine().getTextureManager().loadTexture(bta);

	FileBitmapTextureAtlasSource fileTextureSource = FileBitmapTextureAtlasSource.create(imageFile);
	TiledTextureRegion btr = BitmapTextureAtlasTextureRegionFactory.createTiledFromSource(bta, fileTextureSource, 0, 0, 1, 1);

 
	Sprite s = new Sprite(0, 0, btr,
			gameActivity.getVertexBufferObjectManager());
	s.setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);

 	return s;
}