Well, possibly the gravity well of a black hole is able to partially capture light from 360/360 degree directions that is able to spiral out of the gravity well because it was just not close enough to be caught. Logically, a 'black hole' (or the 'surface' just just outside the event horizon) seen from close up may appear fairly bright, if not brilliant, from the distance shown. And appearances of such a gravity well may appear non-circular given the variety of light sources perceived from source. Really, we must consider all possibilities, not just assume an 'all round knowledge' of all things that require imagination and insight of other possible explanations.
Given the simplest Schwarzschild black hole, the mathematics describing all the observed phenomena (in the APOD) is on solid ground within the framework of general relativity, including non-circular Einstein Rings
. I'm not sure what you meant about "may appear non-circular given the variety of light sources perceived from source". Extended, non-circular light sources behind the black hole are distorted in a very predictable way, and in fact visible in the image. Assuming no accretion process, as is the case for this APOD, no photons can escape so that they appear from within the black region. (But how fuzzy are the edges?)
Although future observations and data approaching 1.5 Schwarzschild Radii (we currently have none) may reveal new phenomena that require revisiting GR, there is no data today to suggest anything "out of the ordinary"
The current GR theory is holding strong and not cracking yet. I'm anxiously awaiting the start of upcoming VLBI observations of the Sag A* (Milky Way's BH) event horizon (or at least to the Innermost Stable Circular Orbit). The telescope consortium is the Event Horizon Telescope a good S&T article about it can be found here