I have installed 2 WP sites in the past 3 days. Both behave similar. Both do not load the front page graphics - the spectacular rolling slicing fx "showcase", but it did load the static picture front page when I themed "yoko".
BTW The only way I can change a theme is within wp-admin / wpmudev has no effect... at least for me.
So either "showcase" has a bug, or I am repeating the same "instal" mistake twice... being a newbie, I could do with some help.