Thinking about this again, there is no reason to have the same file size limit for both avatar and profile picture, even more so considering that they have different image size limits (see quote below). 250 kB limit for the avatar max file size is too high, given that it's limited to 140x140. No .jpg file will use that much space.
I was wondering how my avatar (listed in one of the previous posts) used 175 kB, but it's explained by the fact that it's a PNG and it's 306x306. I must have saved it like that when editing the original one, which is not a square picture. The original one, which is a .jpg, uses a mere 27 kB. As I mentioned before, this also means that the system doesn't convert avatar uploads to a single file type.
I've just done some experiments downsizing large, multi megabyte pictures to .jpg at 140x140 and they top out at less than 35 kB, so there is no reason for the limit to be 250 kB, you can easily set the limit at 50 kB and that will save a lot of bytes per page. People can potentially save up to 2 MB per page at the default of 10 posts per page, up to a whopping 20 MB at 100 posts per page.
In case you want to allow .PNGs too so as to not have to convert them on your side, you can still set the limit at a lower 75 kB, that should cover all of them.
Image sizes for Avatars are at 140x140 (They have been for a little while after this was deemed a good balance when the membership were consulted upon initial migration)
Profile Picture sizes are at 240x240
Avatar Max File Size:250KB
Profile Picture Max File Size: 250KB