I'm thinking pageload speed here. Please combine them into one image, since their link points to the same url anyway.
Secondly, please put
width in its
<img> tag, so that browsers can render the page quicker, and an
alt tag, so that it's valid XHTML.
Lastly, since you've graciously hosted
http://rpxnow.com/openid/v2/widget, why not host this image too, so that it is also cached and reused across all sites who use RPX?