There has been a rendering of SpaceX Superheavy Starship with two additional side boosters. Each side booster would have 31 Raptor engines like the Super heavy first stage.
A SpaceX rocket with this configuration would be able to launch about 250 tons in one launch versus the 100 tons of the SpaceX Superheavy.
Kimi Talivitie is the original creator of a rendering of a metallic SpaceX Super Heavy Starship. Someone else appears to have added the Metallic Super Heavy side boosters.
— StarShip SuperHeavy (@StarShipSH) January 10, 2019
Here is the uncropped rendering of the metallic SpaceX Super Heavy Starship with side boosters.
Here are earlier Kimi Talivitie SpaceX rocket renderings.