How to make the thumbs equal?

Hey guys,

I don’t know what the problem is but my thumbs are not equal.
Here you can have a look http://freeartisticphotos.com/high-resolution-pictures/turquoise-water on top of the large image.

I would like to have all the thumbs equal in size disregarding the fact that the thumb will not display the whole image.

Any ideas?

Thanks!

http://wordpress.org/extend/plugins/contextual-related-posts/