For "grand" meaning impressive, magnificent, or large:
* Humble
* Modest
* Small
* Tiny
* Insignificant
For "grand" meaning pompous or pretentious:
* Humble
* Modest
* Down-to-earth
* Unpretentious
* Simple
For "grand" meaning expensive or luxurious:
* Cheap
* Inexpensive
* Affordable
* Basic
* Simple
To give you the most accurate opposite, please provide more context about how you are using the word "grand."