Hope this is the right place to post this.
Basically, you can rename any file to .png and upload it to vizzed's Photo Album, there's no verification for it actually being an image as far as I can tell (which honestly is a very quick fix).

I've been using this for the past 2-3 years to use external css/php in my layouts, by uploading a .css file with contents like these to the Photo Album, renamed to .png (as can be seen here) and then @import'ing the Photo Album image through a relative link instead of an absolute one, which the URL filter can't detect. Meaning that I just changed the URL from "https://www.vizzed.com/boards/../smd/photo_album_pics/fullsize/281180-1479155328.png" to "/boards/../smd/photo_album_pics/fullsize/281180-1479155328.png", which browsers will look for on the current domain (eg vizzed.com).
The .css file it imports also executes some php on my server, allowing that effect on my layout where the background colors are different on every refresh (and the star tilts slightly differently). This isn't dangerous to vizzed at all since the php is running on my server, not vizzed's, so don't worry. Some other sites that allow for layouts allow this by default, that's how safe it is.
To check the code in the photo I uploaded, just save it to your desktop and rename it to .css or .txt and open it in a text editor.

As sort of a relief, I did try to upload and run php on vizzed using this, but I couldn't get that to work. This is the file I tried to mess with for the record, you can save it just like the earlier file and check out the code, it's just very simple css output.
I didn't really try much of anything else because I figure after the last time we managed to shut the site down you patched out javascript execution and if vizzed doesn't use php then I'd just waste my time trying to figure out what else, but still it might be wise to fix the uploader to actually verify images, just in case.

(edit: This below stuff actually doesn't work because while my layout shows up in the layout editor and during thread previews, it doesn't actually work when viewing a thread, so nevermind that!)
Fun fact: If you click this link, my layout will actually start animating a lot more. You can't put links in signatures on vizzed, so I couldn't put that anywhere, but I figured I'd mention it here to show what kind of stuff remote php enables. (clicking it again undoes it)
Again, harmless because the php is running on my server and not vizzed.

leod : You sir have just earned the most useful user award in my book . I am adding this to my favorite and trying this on my next layout. I've had problems uploading gifs due to size limitation which when I reduce on Photoshop makes the graphics look too pixy. Have you had this problem?

jlove92 : Oh this wasn't meant to be some kind of tip, especially since it seems my layout doesn't actually show up in threads because of this exploit being used anymore. I posted this more so that it can be fixed, since it's clearly unintentional.

It used to work just fine, and it still does show up in the layout editor and when I preview a post, but inside threads it appears to be thrown out (as can be seen in the two posts in this thread) (a moderator can probably check the layout I have equipped right now and see that it works in the layout editor just fine?).
Interesting! But the bug is still there!

leod : There's always a way to get around things specially when coding is involved. I just trying doing what you described and get the same error. I was hoping to find a way around it. I got two layout and hoped this will help me get them finished and working. 
I don't know maybe a new coding on these pages keeps it from working whereas layout editor may have old codes?

leod : I'll summon David for you.

Davideo7 : (Content hidden from non-administrators!)