The above have some very interesting interactions with the comment pages, like darkening out everything, including the comments of others so it's one huge black patch.
A bit of fiddling later from the above suggestions, and I got this:
/*Visible, clickable Blacklists*/
.post-preview.blacklisted-active img {
opacity:0;
}
.post-preview.blacklisted-active {
background-color:black;
display: inline;
}
.post-preview.blacklisted-active:before {
display: none;
}
Blacklists show up as a regular size black box. The image can be hovered over, but only within the actual size of the image so the corners of the black box won't be clickable/hoverable.
The posts will also show up in the comment pages, so the comments are visible, but the image itself is invisible.
I removed the "Blacklisted" text as it is also unclickable, and appears weirdly in comment pages.