this has been discussed quite a lot, so i won’t go into it too much, but asking artists for free work is a bit disrespectful
especially when you’re asking the artist to design them for you.
have you considered using a dollmaker?
https://picrew.me/ has been incredibly popular lately, and has some amazing options and styles available (I used it a couple of times to try out concepts, myself ~)
once you have a simple reference, maybe look around for threads where artists offer their services for free?
or, ideally, look into commissioning someone! there’s really great cheap art out there, and you’ll be supporting the people who are doing work for you