I don't have the slightest idea what you mean when you say "...after you drop down the small-scale, low-SNR noise...".
The 'c;assic' approach to astro-image processing is based on looking at the image as 'the sum of its parts' abd, at the very simplest of levels, every single pixel on the image can be considered as not only having an x and y coordinate, and some form of intensity coordinate, but also to be part of 'another x- y world' where one axis is often used to denpte 'scale' and the other is used to denote 'brightness'.
So, at diagonally opposite corners of this new x-y area we have very bright and very large object - such as the cores of galaxies, etc. And in the other corner we might find the 'background' of the image - containing no stars, just other very dim 'noise' with little or no sense of 'object'.
Taking the analogy further, and moving along the 'brightness' or 'intensity' axis we see the 'sclae' of objects increase. This might be where we would expect to find dim gaseous nebulosity, before we finally 'turn the corner' and see the brightness of this kind of nebulosity increase as we head beack to that first corner that I described.
Of course, if you 'turn the corner again, you remain with high intensity image data, dropping from very large objects down to very small objects - and these, of course, would be the 'stars' in an image.
And, making the last turn, you head back down the 'small scale' axis, reducing intensity as you, until you finally get back down into the world of non-descript 'background noise'.
Hopefully, you might now be able to visualise where your image might be capable of some improvement - it is in this area of small-scale (i.e. no discernible structurs'), low-level (.e. 'faint') noise.
And the trick here is to either lower the intensity-level even fursther, or to change the structure-size so that you can't even really make it out in the first place. And, doing all of this without affecting the remainder of your image (remember, astro-imaging is just like juggling with running chainsaws, it becomes easier with practice - and plenty of bandages!!).
The noise that I was referring to is that 'speckle' that you see when you zoom right in on the fainter areas of the image - think about trying to knock any 'colour' out of this - or aim to leave the colour just on the blue side of a neutral grey (this is down to personal prefeence, of course - but at least try and mute the reds and greens, especially the greens - hence the SCNR Process). Also, imaginne if you could 'blur' the whole of this noise section - smoothing it out if you want to thinks of it that way. Your image might then look more 'glossy' - but, don't overdo things, there is nothing quite as unpleasant as an 'artificially washed out' image, so try to keep things in proportion to how the foreground of your image appears.
I hope my explanation helps, and gives you some ideas to experiment with.
