To comply to W3C standards images must have height and width sizes allocated.
If you want to add that to the images you can add it in: modules\mod_jflanguageselection\tmpl\namesplusimages.php
around line 121 add width and height as below.
$outString .='<img src="' .JURI::base(true). $langImg. '" alt="' .$language->name. '" title="' .$language->name. '" border="0" width="20" height="14" />'
