you can always use an image optimizer/recompressor like FileOptim, pinga, or this fancy web version of ImageOptim to shrink file sizes considerably without having to drop the resolution, and with a minimal drop in quality!

for OSX users there's, well, ImageOptim, and for linux nerds there's Trimage and about a billion CLI tools for it and you already fuckin know about them if you're using linux lmao. these are not the only tools.

however, here's an important caveat: if you're doing pixel art you almost certainly do not want to do lossy (though there is lossless optimization in those tools) optimization, or if you do, you want to be highly conservative with your values, but you're also not nearly as likely to be hitting into those file size limits.