gv seems to use a 50x50 pixmap as an icon. Have a look at the file /usr/share/applications/gv.desktop which states:
To fix this, you could change the icon to /usr/share/pixmaps/mini-gv.xpm (also included in the gv package)
...or any other icon file by editing the desktop file as root:
The same might apply to eclipse. Have a look at /usr/share/applications/eclipse.desktop.
gksu leafpad /usr/share/applications/gv.desktop