What do you mean by characters? For Daz? Look on their store and find someone you like, then either buy it or look in the Assets Release forum here if it's uploaded.
Ren'py is just a programming tool to code a game, it doesn't make art. Daz3D is a popular 3D modelling program where you can buy/pirate premade assets like characters and clothes and then make renders with them (aka the art for your game).