Sorry, I've got no experience making Toy Story stuff, and frankly no inclination. See, I used to customize Star Wars figures, but I kept getting burned by Hasbro. I'd get this inspiration for a really obscure character, I'd buy the two or three donor figures who I needed for parts, spend hours cutting and glueing and sculpting and painting... and then walk into Wal-Mart a few months later, and there would be the same character, costing a fraction of what I'd put into mine.
That's one of the reasons I enjoy customizing Muppets... precisely
because Palisades is so truly and irreversibly defunct! I can create art for myself simply to satisfy my soul, without any worry of being undercut by a corporation.
To me, customizing Toy Story would be about like customizing the little Mattel characters from Cars 2... my guy says sooner or later they're gonna get to them all. And when they do, they make them in several different scales all at once. Just keep searching, eventually you'll probably find them.
But if you really want customs of those characters, why not see if you can find someone who already does Toy Story customs?
I want to say I saw a custom Mr. Potato Head once... it wasn't the smaller size like you want, though. It was made using a regular MPH body, but the customizer had made separate eyes like in the movie. (A real MPH has the eyes as one joined piece, and they attach into one hole in the potato, not two.)
I may have seen it over at Rebelscum's forums, or possibly Micechat's? Look around, use Google, see if you can find someone who has already done some Toy Story customs, and that would be the best person to ask. For instance, look at the bottom of your last pic... who is "Emma in Candyland"? Where did she get that Hockey Puck figure? A little detective work there might yield you some good results.
Oh, and as for the nesting dolls... my first wife once bought a set of blank wooden 'troikas' and painted them as Star Wars characters. This was like in the early 90's, and that store doesn't exist anymore, but there's got to be somewhere to find the blank ones nowadays. I don't think they'd be as small as you want, and from what I recall, the paint eventually flaked off of them, sorry to say. But I bet if you found some blank ones, you could paint them yourself and be far more proud of the results than if you got someone else to do it anyway.
Also, feel free to use my e-mail address for any future off-topic (i.e. non-Muppets) questions.
Ploovo241@aol.com
Getting back to the Muppets... I have a very large custom in the works that I hope to get to soon. It's not a canon Muppet character, but it is something that folks requested to see after they saw certain of my Muppet movie parody figures.
I've had the body ready to go for a while now, and I finally have the head. Anyone care to guess what it is? I'll give you a hint... the character is implied in a photo posted on the first page of this v2 thread, but not seen directly.
Alex