Ask Black-Rose.

Hes not on right know

To start making fakes you'll need sprites. Go to the MK Warehouse to get them. Also read through this thread to get some pointers and feedback about other peoples fakes or artwork in general. It might prove to be useful.

As an added suggestion try messaging a user who you think makes really good fakes. Ask them for some pointers, opinions, etc.

Well, I don't make them in the best way, but here is how I make mine:
I use paint. Yes, windows paint.
Okay this is how you do it, go to mk warehouse, and they have sprites, backgrounds, prop, blood, etc.
Choose the background you want FIRST!
Then put on the characters you want, then the props (fireballs, etc) then at last the blood.

And you make your fake. :)
Hope this helps!