Please do not respond to this post without reading it fully.
I suggest alterations (either generally, or specifically) to help users work around an unfortunate (and I assume, unintentional) limitation when dealing with profile background images.
I’ll explain the situation first, then give my opinion on it.
Here’s the experience:
I could use my “me at my laptop, in my room surrounded by easter eggs from my stories” commission (which is quite suitable) for my profile background. I upload it (no idea what size or file type, let’s say 700kB .png) and it creates a 75kB uploaded and saved background image.
Bam.
Decent quality.
Efficient use of memory and storage; 75kB.
Thumbs up.
Everything seems to be working well.
Now. Problem time.
The image is repeating head-to-foot, and it doesn’t repeat well. Why? It just so happens to be one that doesn’t. I’m sure users can also upload backgrounds that do repeat well, but this isn’t that kind of image; The floor is abruptly cut into by the roof and ‘I’ keep reappearing at my laptop, again and again as you scroll down, It looks dumb, and I look dumb, and the page looks dumb.
OK, so I open my editor and create an elongated version. Just an extra massive lump of single colour ceiling on the top and floor on the bottom (I went into a graphics editor and did this, I’ll post examples on discord).
My image is now 750 x 2200 pixels (extremely tall) and is basically the same image, except with a massively elongated blank floor to prevent the background from repeating and looking dumb.
I upload. Aha, snookered.
I’ve exceeded the 1200px longer side, and now my background is compressed down to a 30kB file, rather than the 75kB file it was previously, simply because of the metrics involved.
My background is now cropped well and it doesn’t repeat no matter how far down you scroll (unless you scroll far beyond my profile’s text and windows, and why would you?)
But now the image is horribly over-compressed to fit the unfair parameters for an image of its canvas shape, and for no good reason. The file is tiny anyways and besides it’s 40% smaller than it’s processor, and besides besides, even that was tiny anyways, and besides, besides, besides, the new elongated version was fairly small before upload anyways (I could easily make it a 150kB jpg with no grevious loss of quality, and I’m guessing it could easily make a sub-100kB.webp of acceptable quality too).
So my choice is unreasonable compression I can’t do anything about to avoid the repeating, or, background repeating I can’t do anything about to avoid the compression.
I suggest one of:
Filesize only based compression rather than longest-side based compression, for either background images specifically, or, images generally because this would be fine IMO; if the issue is file size, make the compression threshold file size, whaddya got against rectangles ova hee?
That, or,
Separate upload parameters for profile background images specifically, like how our avatars have specific upload parameters.
Either of them, or,
A minimum image file size in which images are converted (to webp) only but not rescaled, or, not converted or rescaled at all, or, either of those things but for background images only.