pic problems

You are trying to scale a picture from
300px × 300px,
to 556px × 556px
This will allways return a “muddy” picture.
Try upload it in a higher resolution, and the picture will be better. Otherwise go into the picture settings of wooCommerce or WP itself and change the resolution of the pictures there.
And remember to regenerate thumbnails afterwards.
-Sofus

Yes, under Woocommerce–> Settings–> Thumbnail Settings i think it’s called (mine’s in danish so i try to translate on the fly).
Hope it helps

Tak for example this one: (I can’t read kyrillic, but i’ll try to guide anyway)
http://solti.org/?product=%D0%B2%D1%81%D0%BC%D1%83%D0%BA%D0%B0%D1%82%D0%B5%D0%BB%D0%B5%D0%BD-%D0%BA%D0%BE%D1%88

The HTML is like this:

<li class="etalage_thumb etalage_thumb_active thumb_1" style="display: list-item; background-image: none;">
<a href="http://solti.org/wp-content/uploads/2013/07/vsmukatelen_kosh-300x300.jpg">
<img class="etalage_thumb_image" src="http://solti.org/wp-content/uploads/2013/07/vsmukatelen_kosh-300x300.jpg" style="display: inline; width: 556px; height: 556px; opacity: 1;">
<img class="etalage_source_image" title="vsmukatelen_kosh" src="http://solti.org/wp-content/uploads/2013/07/vsmukatelen_kosh.jpg" alt="">
</a>
</li>

So you take the 300×300 pictures from your media lib and enhance it to 556X556
you need to regenerate your thumbnails:
For that, use this plugin:
http://wordpress.org/plugins/regenerate-thumbnails/