I experience the very same problems. (No icons for the attachments) My distribution ist Debian unstable (sid) and I have the version 1.4.6-3 of the evolution debian package installed. My window manager is kde. Not every attachment is invisible. For example jpegs are shown with the thumbnail. Whats missing is an icon for .pdf files for example. The attachment is just invisible. I tried all the solutions that were described earlier. (installing libgdk-pixbuf, hicolor-icon-theme, gnome-icon-theme) but nothing works. What works and might help you to figure out the problem is to call gnome-theme-manager and select _any_ theme. After that i see the icons. But only for the one session and it totally screws the fonts and keyboard settings under kde till a restart.
With this information, I was playing around. I asserted that starting the gnome-theme-manger, selecting a theme and closing the theme-manager leaves a process called 'gnome-settings-daemon'. When this process is running, the attachments are shown. So, I added a line to start the gnome-settings-daemon before startkde in my .xsession. The gnome-settings-daemon doesn't screw up my fonts and keyboard settings in KDE, I cannot follow your problem. Thank you for this idea :)
Regards,
Gerhard.
