I know there is a thread, but this post is pretty big and I'd rather it not get buried among them. So, here are a list of options, that can even be mixed in some cases;

Option A: Bring layout mods, with new background options that help reduce clashing. Yep, just moderators who do nothing but moderate layouts, logos and themes. Every background that would get submitted would have to be verified by them. If the submitter is found to be consistently good at it, they no longer need to be verified. They would also have the power to edit layouts of all games in the case of color-scheme disasters, and those who apply would need a portfolio or history of making good layouts. I am 100% willing to do this.

Additional options to edit backgrounds that reduce distractiveness can be added, such as dimming, desaturating, basic hue filtering and lowering contrast - with a level to apply them. This helps a lot against clashing. Backgrounds can be previewed before submission. GIFs wouldn't work with this, but they're such an outdated format that little editors used anyway (I'd rather it be applied to the image because applying it on the page could be draining on the CPU, especially mobile users).

Option B: Make banners more customisable and provide guidelines, and provide different customisation versions for light and dark layouts -OR- Make dark/light layout surroundings automatically adjust in accordance. That way we should be able to have some more layout editing options back.

Banner customisability options such as tile instead of upscale would be so much better for pixelart. At the moment it gives you an ugly blurry mass.

Have banner guidelines so I know what should look the best and instead of a very cropped/distorted image.

Option B is not my favourite, but it seems far more likely to go through.