Hi... To solve this problem you need to do a little image editing first.
So first of all you need to remove the background from your original image. You can do this in CrazyTalk itself but you will get best results using an image editor (Photoshop, Gimp, Affinity Photo etc.). Once you have done this save it as a new image.
Then using the original image you should either remove the head leaving just the background (Again most image editors have tools to do this), or alternatively you could just slightly reduce the size of the original photo, then save it as a new photo, and then load it as a background behind your character head in CrazyTalk.