I'm just getting into trying to reproduce my own vintage backing cards and below is my first attempt.
I got a scan of a Luke/Bespin card and replaced everything on it except for the actual picture...the original card was for the Arena mail away special but I changed it to a mail away Admiral Ackbar special. I have changed the title of the figure to "Cloud City Trap" which I think ties in well with Ackbars most famous line haha
I copied the back of the card off a Mail away Nien Nunb figure.
All thats left now is to glue and press the two sides to some card and coat it with a light gloss coating to give it the 'store' look, I am just going to use a bubble from a newer figure and also have to give the Bespin Luke figure I got for it a bit of a spruce up then hopefully it'll look all good....the card is a lot darker but the pictures didn't come out to great.
I've done a bunch of these in the past - a tool that I finally invested in that you might find useful is a round-corner punch (pic attached)...I think I picked one up at Warehouse Stationery. It'll give you perfectly round and perfectly aligned round corners every time.
My brother used to have a wind-up walking ET figure, but I don't know what happened to it.
I didn't make it (it may even just be a Photoshopped image), but I like this custom card idea ...
(Sorry about the hopeless image - it was the best a quick Google seach could come up with. I think I've got a better image on my Mac when I turn that on later.)
It reminds me of the old computer adventure game Hitchhikers Guide to the Galaxy we had. It came with a few extras in the packaging - one was belly button fluff (a small ball of cotton wool) and the other was a microscopic space fleet (an small empty plastic bag).