The angular distributions of Ne7+ ions transmitted at various kinetic energies of 7-70 keV through muscovite mica nanocapillaries of rhombic cross section are measured. It is found that the transmitted ion beams form a rectangular shape at tilt angles that are small compared to those given by the aspect ratio, i.e., the capillary geometrical opening angle. This shape is retained for all ion energies, but its size changes. The time evolution of the transmitted angular distributions shows that the characteristic profile occurs instantaneously and remains in the stationary state of the transmission, whereas it shifts with the increase of the accumulated incident charge. At tilt angles of the capillaries larger than their aspect ratio, the shape in the transmission profile gets distorted from the rectangle by the deposited charge. Combined with trajectory simulations we show the observed shaping effect is due to the image force seen by the ions, interplaying with a deflection by the deposited charge on the capillary walls.