Well, to create a custom VRC7 patch, you've got to select set #0 and then you can customize the settings of the frequency sysnthesis to create different sounds. But beware, since you can only use a single custom set at a time. So, you'll limit yourself when you use this custom instrument just for a slight background track.
Maybe just play two pianos simultaneously a little off-pitch (P80 and P81/P82) and/or on different octaves to create a different sound.
I personally don't really know the difference between Piano and Grand Piano, so I don't know it that helps.
Welcome to the forums and good luck

(although I'm not really a fan of the "Swag" in your name, nothing personal ^^ )