Products and own characteristics

Hi Nicolas, I have a new problem.
I added the characteristics to products of my customer; of course, because it's a shoes brand, I added the numbers.
Well when Hika shows products, without any choice, appears this!

Isn't Ok.

Also, if I change measure, Hika shows a photo smaller ! .

The cart is correct. .

If I change the characteristics like this: ,

I get this:

This isn't good.

and cart is like this:


I would this, on the page products

and this on the page cart

Is't possible! How?

Thanks in advance
Massimo

Perfect but this problem remains:
enter into product show:

change char (the image is smaller than before):

www.inabox.it/gt (the site is still in production).
Choice english language, shop on line, spring/summer, Alice (is only model with measures, at the moment).
I set width thumbnail to 300, this is correct for product list and first product page.
Don't works correctly if you change the measures.
If you want go to admin panel this is to access: