Dear jdchess,
You can check this css file: pluginssystemjat3jat3base-themesdefaultcsstemplate.css
.t3-logo-light a { background-image: url(http://static.joomlart.com/t3/logo/t3_logo_light.png); }
.t3-logo-dark a { background-image: url(http://static.joomlart.com/t3/logo/t3_logo_dark.png); }
.t3-logo-light-sm a { background-image: url(http://static.joomlart.com/t3/logo/t3_logo_light_sm.png); }
.t3-logo-dark-sm a { background-image: url(http://static.joomlart.com/t3/logo/t3_logo_dark_sm.png); }
it will show T3 logo light or dark depends on you set in Template Manager > Your_Default_Template > Profile tab > Footer T3 Logo
http://easycaptures.com/fs/uploaded/572/1321438931.png
Regards.