A method implemented at a user terminal during a video call conducted with at least one further user terminal over a communications network, the method comprising: displaying a user interface on a display of the user terminal (102, 108) for display of received video frames; and detecting selection of a selectable button displayed in said user interface by a user using an input device (206, 208, 204) of said user terminal (102, 108); characterised in that the method comprises: receiving a plurality of drawing inputs whilst the selectable button is in a selected state, each drawing input defining image data to be applied at a facial position on a first side of a face of a user displayed in the received video frames; for each of the plurality of drawing inputs, determining a further facial position on a second side of the face, the further facial position on the second side of the face being symmetrically opposite to the facial position on the first side of said face; for each received video frame, the method comprises: for each of the plurality of drawing inputs (i) determining a position of the face in the received video frame by executing a face tracker algorithm on a processor of said user terminal (102, 108) to determine the locations of the facial position and determined further facial position on the face in the video frame; and (ii) modifying the video frame by applying the image data to the facial position on the first side of said face and to the determined further facial position on the second side of the face; and displaying the modified video frame in the user interface. displaying a user interface on a display of the user terminal (102, 108) for display of received video frames; and detecting selection of a selectable button displayed in said user interface by a user using an input device (206, 208, 204) of said user terminal (102, 108); receiving a plurality of drawing inputs whilst the selectable button is in a selected state, each drawing input defining image data to be applied at a facial position on a first side of a face of a user displayed in the received video frames; for each of the plurality of drawing inputs, determining a further facial position on a second side of the face, the further facial position on the second side of the face being symmetrically opposite to the facial position on the first side of said face; for each received video frame, the method comprises: for each of the plurality of drawing inputs (i) determining a position of the face in the received video frame by executing a face tracker algorithm on a processor of said user terminal (102, 108) to determine the locations of the facial position and determined further facial position on the face in the video frame; and (ii) modifying the video frame by applying the image data to the facial position on the first side of said face and to the determined further facial position on the second side of the face; and displaying the modified video frame in the user interface. for each of the plurality of drawing inputs (i) determining a position of the face in the received video frame by executing a face tracker algorithm on a processor of said user terminal (102, 108) to determine the locations of the facial position and determined further facial position on the face in the video frame; and (ii) modifying the video frame by applying the image data to the facial position on the first side of said face and to the determined further facial position on the second side of the face; and displaying the modified video frame in the user interface.