If you don’t add an image to your podcast's episode, iTunes will use your SoundCloud profile image as the default image for the episode. You can add individual artwork for each episode by uploading an image on the episode’s edit page. Make sure your image is 1400x1400 pixels, or iTunes will not populate the image.
Your individual track descriptions will be visible for each episode within iTunes. Once your listener has subscribed and downloaded the episode, the description will appear underneath your episode's title.