kk game design is a major interest of mine. Unfortunately I am hopeless in art.
Binding of Isaac is a game styled on the old 2 stick arcade games. The graphics are also styled after that sort of game, though polished and high res for modern standards. Looked at a couple videos and the art style is very simple, a lot of characters are just circles. The art style seems cartoon like, solid colours, black borders for items, an over the top feel.
Star your game, what sort of mood and setting is it? Will it also be an over the top horror, arcade style game? Or will it be a bit lighter, more of an adventure feel? I'm guessing you want the oversized head style of character done. Do you want "retro" low res graphic or nice and smooth, high res art?
Also as a start what specific character designs would be good for a sample? Protagonist? Specific monsters? Any world art? Any specific items or colours that should be used on those designs? Oh yeah if you do you low res art, what resolution and pixel size are you looking for? High res stuff can be scaled but for low res stuff this is important.
/sigh this is the stuff I would ask lol, but again can't draw.