We do not currently offer the ability to insert images into Choice field options. However, this is a feature we are considering for a future release.
Alternatively, you can insert each image into its own Content field. Simply add a Content field to your form, and select the Insert/edit image option from the formatting toolbar. In the dialog that appears, you can upload your image or include the image url. Then, use the Show This Field - When option in the Content field settings to conditionally display the image when the corresponding choice is selected.