#3 Copy the WWE Championship
This may look familiar. Essentially, it's exactly the same as the current WWE Championship but with "Universal Champion" text underneath it.
There are two sides to the argument with this, with one being that the world titles on the two brands should be equals to each other and don't need to stand out as different, so why would it have to have a different design?
Alternatively, if you're opposed to the idea of it looking exactly the same, the way to get around that is to alter the WWE Championship itself.
It's somewhat strange that the WWE title on SmackDown has a red and black design as opposed to something with blue, doesn't it?
If the Universal Championship had the WWE Championship's current belt layout, then the SmackDown WWE Championship could be tweaked to look like this as a response: