The icon shows for applications installed from rpm, but a default icon is shown for not installed applications - i.e. eclipse downloaded manually from their site, unzipped and ran. This issue appeared after the last kde update, before everything appeared just fine.

journalctl shows this kde/plasma related packages being updated in Sep 23:
kde-l10n;14.12.3-8.fc22;noarch
kde-platform-plugin;1:4.11.22-2.fc22;x86_64;updates
kde-workspace-devel;1:4.11.22-2.fc22;x86_64;updates
kde-workspace-common;1:4.11.22-2.fc22;noarch;updates

... and these were updated in Sep 21
kdeplasma-addons;5.4.1-1.fc22;x86_64;updates
plasma-desktop-doc;5.4.1-2.fc22.1;noarch;updates
plasma-nm-vpnc;5.4.1-1.fc22;x86_64;updates
plasma-nm-pptp;5.4.1-1.fc22;x86_64;updates
plasma-nm-openvpn;5.4.1-1.fc22;x86_64;updates
plasma-nm-openconnect;5.4.1-1.fc22;x86_64;updates
plasma-workspace;5.4.1-3.fc22;x86_64;updates
plasma-desktop;5.4.1-2.fc22.1;x86_64;updates
kde-platform-plugin;1:4.11.20-2.fc22;x86_64;updates
breeze-icon-theme;5.4.1-1.fc22;noarch;updates
plasma-systemsettings;5.4.1-1.fc22;x86_64;updates
kde-cli-tools;5.4.1-1.fc22;x86_64;updates
plasma-milou;5.4.1-1.fc22;x86_64;updates
plasma-breeze;5.4.1-1.fc22;x86_64;updates
kde-style-breeze;5.4.1-1.fc22;x86_64;updates
plasma-breeze-common;5.4.1-1.fc22;noarch;updates
plasma-nm;5.4.1-1.fc22;x86_64;updates

I also tested with the "Icons only" alternative of the task manager applet but with no success.

Reproducible: Always

Steps to Reproduce:
1. update to latest code
2. download eclipse or other software
3. unzip and run

Actual Results:  
the task manager shows a default "executable" icon instead of the eclipse icon that appears in the title bar of the application

Expected Results:  
the icon in the task manager should be the same with the one shown in the title bar of the window