Return list of files in `c` that are images. `check_ext` will filter to `image_extensions`.

def get_image_files(c:PathOrStr, check_ext:bool=True, recurse=False)->FilePathList:
    "Return list of files in `c` that are images. `check_ext` will filter to `image_extensions`."
    return get_files(c, extensions=(image_extensions if check_ext else None), recurse=recurse)