Get the Line Creators Studio app
You can take pictures or upload photos to use as stickers. You can also cut around the photo to use just the main image.
You can also add text.
Here are some examples of what I did.
I tried some hand drawn ones and I used the IbisPaint app to fill in the colors. It was pretty easy actually.
Here are some examples of using IbisPaint. It took me about 2 minutes to do this.
There are various tools.
After you finish you upload the picture to the Line Creators Studio and you can change the picture to your liking.