There certainly are telescopes that capture images of objects so faint we have to wait long periods of time just to catch a few photons. This is enough to do so

There certainly are telescopes that capture images of objects so faint we have to wait long periods of time just to catch a few photons. This is enough to do some interesting astronomy, perhaps surprisingly. If you have a big enough telescope and point it at something long enough, you can almost always resolve it better than just one pixel. There is one hard physical limit though. Due to the expansion of space, there are in fact objects so far away that their light will never reach Earth---one might say that space is expanding them away from us at faster than the speed of light. And because this expansion is actually getting faster all objects are actually accelerating away from us. That means all the time, there are objects that speed up from sub-lightspeed to super-lightspeed as they move away from us. Once they cross that lightspeed barrier, their light can never reach us again. So it's concievable that we might just happen to capture the last photon of some object that will ever reach us. In that sense, then, some objects are indeed so far away that for a brief period of time, any image of them can only hope to be a single pixel, no matter how good your resolution or magnification.