Are you using 3.2 or 3.4? This is for 3.4. This might fix it for 3.2:
in the .icon-grid section around line 669, add -shell-grid-item-size: 106px;
in the .contact-grid section around line 757, add -shell-grid-item-size: 240px;
Sorry, I'm using 3.4 and so deleted the deprecated stuff I don't use
Although I have actually seen icons not appear in 3.4. Restarting shell seems to fix it. Not sure what that's from.