Could try this
HTML Code:
img.alignleft {margin: 0 20px 10px 0 !important;}
img.alignright {margin: 15px 0 10px 10px !important;}
which only has changed numbers for existing code.
Numbers are in this order http://www.htmldog.com/reference/cssproperties/margin/ Nice to know when fiddling.
This should actually only go for images in content since you might use img.alignleft/right elsewhere - and there you dont want extra margins.
Not sure you need to but to fix that I think you can add either of these
.entry-content
#content
#content p
before img.alignleft or right, example: #content img.alignright
That got complicated fast, heh but you get the idea? Isolate extra padding/margin to where it is needed - if that is a problem, probably is not!