Ok so this is not exactly what youre asking for. But if you want as much image space without UI parts, you could follow AnnieMay’s excelent post on tweaking the AChat GUI.
https://www.funnyadultgamesplay.com/forum/index.php/topic,2338.0.html
So far I’ve downsized and moved the Rate and Gift buttons, (a.)
Moved all partner pic and excitement bars down to the old Gift button location (b.)
Moved the Leave Room butten to the right (c.)
The last one is abit fucked up cause now I covers the Full/Windowed icon of Windows. So once I go full screen, I cant go back to windowed anymore. Have to use AltTab.
If you only want to ‘black out all but the people in the frame’, you can use the buttons ‘Hide Room’ ‘Show Room’. But im not sure if that’s what you meant.