If you want to stick with brickbreaker elements rather than hybrydising with other genres, perhaps think of (1) powerup elements or (2) level elements that change things up a bit and add a bit of freshness.
Not sure what you currently have, but additional elements could be;
-Teleporter nodes, transporting the ball from one area to another, could be used in boss battles
-Cannon pad, ball enters and is fired at speed in a random direction (could be helpful or a hindrance)
-Gravity nodes that exert a pull on the ball
Powerups:
-Mega ball, short timescale powerup that increases the size and it crushes through most bricks bar unbreakables
Enemies;
-Some brickbreakers have enemies that hover around the play area, and introduce some chaos into the mix
All of these things are quite modular, so you can mix and match within the levels to try and provide more variety.
If you wanted to push the boat out, you could try and put a two player co-op mode in, one paddle above the other, where either player has the ability to press a button and switch from front row to back row.
I guess it mainly depends on what you currently have, and how far you want to take the project.