Adjusting the size of images in forms

My KoBoToolbox survey includes many media files (images) embedded in the form. Respondents have to view these images and make choices based on the information contained in each image. My issue is that the images are currently to small for respondents to see the level of detail required. I have tried to resize the image files in Microsoft ‘Photo’ by manually changing the dimensions and then re-uploading them to KoBoToolbox. However, no matter how much I enlarge the images using this method, the size of the images does not change when I actually deploy the form. Am I reaching some sort of maximum size limit for images in KoBoToolbox, or is there another way to increase the size of each image?