I am used to OSX which lets you do this, and its very usefult to me because I always have at least three terminals, so having a different look for each makes my work easier.
Also, is it possible to download terminal 'themes', or I have to manually define the styles from the terminal options?
P.D: I am using a Xubuntu environment
To open a new terminal with a different profile, use File->Open Terminal->Profile name.
You can edit the different profiles under Edit->Profiles..., or just edit the current profile with Edit->Profile Preferences.