Feature Image size

Hi Is it possible to resize the feature image on two different pages? On the main page I'd prefer it to be smaller and in a bit from the left hand side http://art.dawnbeer.co.uk/blog/. I'd also like to remove the lower horizontal rule from this page. The image on the post page is very large and I would like this to be smaller if possible. http://art.dawnbeer.co.uk/new-work/ Many thanks