I then upload the xml form on my Android device and create the media folder where I store the Praziquantel.png image. However, when I then complete the from on the ODK collect app, the image does not appear. Do you know why this is happening?
Try deleting the ::English from the column header. You should only include the language identifier if your label (and other translatable columns) also have a language identifier. See this post for more details: