'nouveaux' is the masculine plural form. So you could say; 'J'ai nouveaux chevaux' - I have new horses.
Nouveau - Nouveaux Nouvelle - Nouvelles
This is a very common pattern in French. And always keep in mind (I've actually studied French for over a year now) that adjectives must change according to the noun they are describing. It's something I still forget to do to this day.
This site explains the few adjectives which come in front of the noun in French: http://french.about.com/od/grammar/a/adjectives_4.htm
Apparently you use the form 'nouvel' when the word following it is masculine and has a vowel or non-pronounced 'h'.