This is not an LXDE bug. Themes must support the background for panels, with colour definitions or using pixmaps. If the first theme worked, Lubuntu-default, it's obvious that your panel is working fine. Does those downloaded themes support newer versions of LXDE?
** Changed in: lxpanel (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1352962 Title: Not transparent system tray icon on LXDE To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lxpanel/+bug/1352962/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs