General Synonyms:
* Modest
* Humble
* Simple
* Plain
* Low-key
* Unpretentious
* Down-to-earth
* Unpretending
Synonyms Emphasizing Lack of Pride:
* Self-effacing
* Humbly
* Without ostentation
Synonyms Emphasizing Lack of Attention:
* Inconspicuous
* Unremarkable
* Undemanding
* Discreet
* Quiet
The best synonym will depend on the specific context in which you are using the word.