If you don't mind tips/resource sharing: sometime last year I got my hands on Heroes of Legend and it's great! If you have completely no idea for NPC or PC or would just like to add some background quirk, that's the book to help with it. I don't know about you, but the format is just ideal for me. You roll on a table, get one or two sentences worth of description and that's your writing prompt.
What makes this book different from quite a lot of the resources is that there aren't just terrible or amazing things. It also points to some things that you might not have thought about from mechanical standpoint (lost an ear: penalty to hearing, advantage in wrestling/grappling). There's also background section for your parents, important figures, childhood adventures and friends, small vices etc. Basically, all those things that you know that a well-developed character should have but not always bother to develop more than a word in passing… have I mentioned that it's a great book? :P