Here's a link to an interesting Jira that was passed my way today. SL resident Alison Alena made some small tweaks to the SL avatar mesh that improve the geometry without affecting your ability to use SL avatar content.
What's this mean? A more natural looking body shape that isn't nearly so distorted by poses and animations, and you can make this improvement yourself without affecting your ability to use standard SL avatar content like skin and clothing textures. Particularly it reduces the unnatural mid-torso "fold" and the way your butt and legs distort when animated or posed.
Simply download the ZIP file attachment to the above Jira and install the files in the appropriate SL viewer directory. Kim Link's comment explains how, at least for Windows users like myself. Just look for the viewer directory under the Program Files or Program Files (x86) folder in your C: drive. This fix works for any and all SL viewers ever made.
Not only will it fix your own avatar, but every avatar you see. Of course, this fix only works for your personal experience, be sure to tell everyone about this fix so they can enjoy the improvement!
Also remember to both "watch" and vote for the issue to let Linden Lab know you'd like to see them include this fix in the standard SL viewer.
Believe it or not there are other fixes like this LL could introduce. Camilla Yosuke posted this gem years ago, but few people seem to talk about it. Basically, she adjusted the vertice weighting on the avatar's inner thigh, getting rid of the ugly distorted texture area there. Unfortunately she didn't include any files we could download and try on our own.
Be sure to watch and vote for that, too.
Ideally, LL would provide an all new avatar mesh for us to migrate to, allowing us to continue using the old mesh for legacy content as we moved forward in creating better content. Still, small fixes like this are better than nothing.