So I am trying to figure out how to apply images to every mob in the game... However I am not sure how to do this. I know how to apply an image to a single mob, but not to every mob. I also need to be able to delete the image once a certain requirement is met. Can someone help me shed some light on how I would go about doing this? Thanks in advance.
You would have to create an image for every single mob to apply it to them. Now if you mean show an image to every single mob then something like this would work:

In response to ExPixel
Yes I DID make an image for the mobs I wanted the image to be over. HOWEVER, the only way I could think of to make an image for every mob in the game doesn't allow me any control over removing the image from the mobs once the requirement is met. I DO know how to allow any/all mobs to see an image.
In response to Taijutsu Lee
Give the mob a variable containing the image =|
In response to Taijutsu Lee
Give every mob a var to store what image is attached to that mob. Then, you can easily access that var to find an image attached to the mob.
Another way is to make a list and store all of the images in it for later access.
In response to Complex Robot
Thanks for the help guys, I managed to find a different way to do it. I made a list for the source of the proc that was putting images on every one, and adding every image I made to the list... I tried this earlier, but it didn't work on account of me forgetting to make it so that the "src" of the proc could see the images haha... Plus, putting in the list made it so I could access the images from the "src"'s vars, rather than checking every mob in the worlds vars.

But again, thanks for the help!