Add a flag icon to link corresponding to the hreflang attribute.
Well, no :(
hreflang Flag uses the same technique of setting the css background of the a tag, so the displayed icon will be the last css match (probably the flag) you have to choose one. There could be a possibility as described here: http://www.quirksmode.org/css/multiple_backgrounds.html but this only work on webkit based browser. However this is not implemented in hreflang Flag now.
Please see plugin homepage: http://silicone.homelinux.org/projects/hreflang-flag
Or search wordpress.org Forums.