Generally, you should try to keep your photos as attractive for the host family as possible, meaning that they reflect your personality and that they are appropriate.
Don't include any revealing photos and make sure that you are decently dressed on your photos! The host family is also not interested in your party pictures or pictures of your tatoos and piercings. Think of the photos as photos you would send a future employer, because that is what your host family ultimately is.
Include photos which show how you are playing with children. If you don't have any, leave them out. Don't stage them. Try to make your photos appear normal and effortless.