Each year when November rolls around I consider doing NaNoWriMo, and each year I discard that idea, because it isn't really the way I write. At all.
But this year, I am doing the 30 Characters Challenge. Draw or write character sketches for thirty new characters, one each day for the entire month, and ta-da! You have a library of characters to use in current or future projects.
If you'd like to take a gander at who I create this month (character profiles with inspiration images, since I can't draw a nice stick figure), my profile is here. There's already tons of amazing art and stories on the site.