Actually all the skins on that page are way outdated and have not been maintained as changes have occurred over time in the mojoPortal skinning system. I've just locked that page down since it has no useful content. Sorry for the inconvenience.
The only up to date skins are the ones shipped directly with mojoPortal and the ones in the extra-skins.zip on our codeplex download page. We don't have thumbnails for those either, however. Maybe a community member would like to volunteer to make thumbnails, it isn't something I have time to do myself. It would be ideal to have some kind of skin gallery, but it is also a lot of work to implement and maintain such a gallery. We also need some good designers to volunteer to make some nicer skins. I've made most of the ones we ship myself and that is not a good thing because I'm a developer not a designer, and unfortunately people often judge the CMS by the included skins, but design is completely de-coupled from functionality and people should judge it only on the functionality since any design can be implemented by a good designer. But then again I also think any important site is going to need a custom design rather than any pre-made design that is not unique, I'm always surprised when people actually use the skins we ship.