Add classes to img element?

Is it possible to add classes to images with the Styles dropdown? Or does that feature only work with divs, paragraphs and spans?

That is, can I put something like this in my fckstyles.xml...

<Style name="img-left" element="img">
<Attribute name="class" value="img-left" />
</Style>
<Style name="img-top-left" element="img">
<Attribute name="class" value="img-top-left" />
</Style>
<Style name="img-right" element="img">
<Attribute name="class" value="img-right" />
</Style>
<Style name="img-top-right" element="img">
<Attribute name="class" value="img-top-right" />
</Style>

I'm finding that these styles only appear in the Styles dropdown if I change the element from img to div, p or span.
Thanks.