I can confirm that this appears to be related to the current theme. I am missing icons on multiple computers and I have never run KDE on these systems. I tested all the out of the box themes. Below is a list that appear to be missing icons in Ubuntu's Software Center. Oddly, while Clearlook is missing icons, Human-Clearlooks is not.
Clearlooks High Contrast Inverse High Contrast Large Print Inverse -- Software Center is missing several icons in KDE/Xubuntu https://bugs.launchpad.net/bugs/527503 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs