It is relatively painless to change the dimensions of the surrounding border for themes. That said, you may end up with a gaudy looking heavy window, but I assume that you don't care about that.
To change border widths, simply open up the theme's Metacity XML file. For example, Human's theme is located in /usr/share/themes/Human/metacity-1/metacity-theme-1.xml
The stanza in question should be apparent:
<distance name="left_width" value="5"/>
<distance name="right_width" value="5"/>
<distance name="bottom_height" value="5"/>
Try mucking with the values until you get something you are happy with. Unfortuanately, resolution dependency still plagues much of Gnome.