Comment 18 for bug 424822

The problem is that in the menu file (e.g. .local/share/applications/alacarte-made-3.desktop) has multiple entries for the icon. Changing the icon in alacarte changes the "Icon[en_US]" entry, which appears in the original menu...that works OK. However in the Favorites folder the "Icon" entry is picked up...if you change that by hand, then the correct icon appears in the Favorites folder.

I notice, parenthetically, that there's a similar situation with "Name[en_US]" and "Name" and that's probably the cause of bug 505600.