IE has always had a quirk about images. Unless you put the tags together with no white space between them:
IE will put some in there. Technically, this is correct as, an image is an inline element. As such it is like text. If you have a space between two letters in your markup, you see it in the layout.
<img src="some.gif"><img src="another.gif">
If you have this:
There will be no space between them vertically, as long as there are no trailing or leading spaces on the lines in the markup.