Graphics/Sprite Creator options

Hey, i'm still really new to the 2D engine and was wondering what everyone uses for thier graphics, whether it's a sprite creator program or anything else. Personally i was thinking about using adobe illustrator for the basic image and then taking that and using my wacom tablet with the art program it came with to do the details. Is that even possible to do? Or does it have to be sprites, or make my image the way i want and convert it with a program or something?

Main reasons i want to use illustrator is because i've been doing graphic design with it for awhile now and love the positive/negative art i can make with it. But if there is something way better to use please suggest it, i really appreciate all the help.