Thanks, it was me, not you. I was thinking you wanted to use CSS to control image size instead of modifying this
<script>
Discourse._registerPluginCode('0.8', function (api) {
api.changeWidgetSetting('post-avatar', 'size', '90');
});
</script>
I’m pretty sure I have seen JavaScript for using categories in conditional checks, but it will take me a while to track it down, if it exists.