To find the right minis for your expansion can be quite a task. Maybe even more so with Non-Star Wars decks. So this page is supposed to help get you started finding the right figurines for all the decks you want to add to your collection.

• No matter what minis you are looking for Miniature Market and of course ebay are always a good starting point.
• A great start for expanding outside the Star Wars Universe is the Game of Thrones expansion set. Good news is, there are actually a bunch of minis available for that world. The miniature game A Song of Ice & Fire:TMG , published by Asmodee already offers tons of expansions and miniatures for the world of Westeros. 

• If you are more into Superheroes, you should definately check out the Atomic Mass Games' Marvel Crisis Protocol Miniature Game for Marvel heroes and the DC Universe Miniature Game for your DC Superheroes

• Knight Models also has a broad collection of Harry Potter minis for the Harry Potter Miniatures Adventure Game.
• You can also find many minis for the Lord of the Rings expansion. There is a Middle Earth Tabletop game series where you can gets lots of miniatures for that world.
• If you are looking for minis to use for other expansions like the Legend of Zelda, Sereinfly for example, you probably need to go the 3D-Printer way. But you already can get many free 3D-models at Thingiverse and only need a service to print them for you. Usually should not cost more than $10-15.
• For other 3D design pages, printing services and sources of Star Wars minis check out the Figures page on the Star Wars Wiki.