For reference we offer resolutions up to 3200x2000 right now.  4K has a resolution of 3840x2160 being the consumer standard. There are some people out there starting to float 8K (7680x4320 !!!) as a thing and while it sounds ludicrous now, there was a time when 4K was crazy. But we also have to remember some people have multiple monitors and may want to span their wallpapers across multiple 4K monitors anyway. Really, I'd like a solution where we can reasonably bundle 8K wallpapers as well to be future-proofed.

The main problem I think we're facing (and the push-back we'll see) is filesize. Right now we're using PNG format images, and depending on complexity the wallpapers have run filesizes between 10-30MB. A 4K wallpaper runs about ~3MB on its own (for skylight), a pretty big hit... But encoded in JPG at 98% quality we halve it to 1.4MB, where I think 8K would become feasible too. Even then, we can encode these ultra-high-def images at slightly lower qualities as pixel-level compression artifacts becomes less visible on these screens.

There were issues with JPG and configuration hardcoding stuff, and because of how we release software, we may need to wait a release or two for 4K/8K wallpapers if we wait for JPG. I'll light some fires under people or try to get some patches in to begin correcting this. Right now the way we distribute wallpapers will cause size complaints if we include them as we do now; we need to fix that first, I think.

Couldn't we distribute the wallpaper in SVG?

(In reply to Aleix Pol from comment #2)
> Couldn't we distribute the wallpaper in SVG?

If we can do it, I'm all in for using SVG straight from the tap; it was something I brought up before during the Plasma Sprint, but I didn't get an enthused reaction. Performance concerns were cited.

Maybe we could have the system check for a named scalable file if the screen is larger than the largest provided PNG wallpaper. If you're using a lower end computer then the PNG graphics might be faster, but if you're running the kind of screen with 4K resolutions it's less of a concern - you probably have the horsepower to render/cache the image anyway. If we do this, we can probably drop the higher resolution wallpapers as well and save some space. 

My one question would be how this might affect the splash or locks screens; could they also use SVG images?

Sure, I'd suggest to just try it. It's definitely possible as long as the SVG's use the QtSvg supported subset. Otherwise, it will start to get a bit more complex.

For Plasma 5.10 and beyond I've added 1900x1200 wallpapers to the build/sizing script. For the SVG stuff I think I'll defer that until later, as if we switch to SVG at some point, it limits what we can do in the future... And it's off-topic anyway.

Shoot, just replied to the wrong bug. Either way, 4k wallpapers are included now anyways.