Move image thumb in post excerpt

This is a really great theme, but the only thing that’s bothering me is how big the post excerpts are when you add a featured image. On top of it being hard to properly adjust the size of the image thumbnail (I don’t know how it chooses what to resize) the height of the excerpts can get a little overwhelming.

Is there any way to move the image thumbnail to the left side of the excerpt, for example, in order to get a more compact design?