This has it working for me. I need to test it with my other "guest" avatars to be sure:

li.Voice_voiceState__OCoZh:not([data-reactid*="123456"]) { }

.Voiceavatar_htiqH{ content:url(https://cdn.discordapp.com/notalk.gif); height:auto !important; width:auto !important; border-radius:0% !important; filter: brightness(100%); }

.VoiceavatarSpeaking_lE+4m{ content:url(https://cdn.discordapp.com/talk.gif) !important; border-color:rgba(0,0,0,0) !important; }

u/keyframes speak-now { 0% { bottom:0px; } 15% { bottom:10px; } 30% { bottom:0px; } }

ul.VoicevoiceStatesa121W {margin: 0 !important; padding: 0 !important;} li.Voice_voiceState_OCoZh{ position: static; }

div.Voiceuser_8fGwX{ width:100%; text-align:center; position: absolute; top: 2%; }

span.Voicename_TALd9 { font-size: 52px !important; padding: 5px 15px 10px 15px !important; border-radius: 10px !important; }

body { background-color: rgba(0, 0, 0, 0); margin: 0px auto; overflow: hidden; }

Keeping the display:none on the very first line was causing an issue with my avatar not displaying at all so I removed it. I'm not 100% sure if that's going to cause additional problems down the line.

My snippet includes the CSS to put the nameplates above my characters head. If that's not something you do you would need to remove the div.Voice_user__8fGwX line and change the span.Voice_name__TALd9 line to {display:none;}