Continuum image (contours) of the Seyfert 2 galaxy NGC 5252 (type S0). Greyscale is an [OIII] image superposed. Note the elongated, even bi-conical, form of the ionized region. [Figure from Peterson's AGN book]
Neutral Hydrogen emission around NGC 5252. Clearly, HI exists throughout the galaxy, and the elongated line emission does not arise because gas is only present along that axis. [From Prieto & Freudling 1993 o-link]
Color composite of the central regions of the Seyfert 2 galaxy NGC 1068. Green is the [OIII] emission line which shows a one-sided conical form. The region within the black square has been studied using the VLT interforometer at mid-infrared wavelengths, and found a compact elongated source about 2 parsecs across, thought to be the "obscuring torus".
A zoom in to the HST [OIII] image, showing the cloudy structure with overall conical shape.
[OIII] image of the Seyfert 2 galaxy Markarian 573 showing approximate bi-cone geometry. In this case, the emission "shells" are also related to the (relatively weak) triple radio source. [Ferruit et al 1999 o-link]