There were no icons in the tab headers for Safari 5 or 6 either.
It's possible that you used something like Glims, which modifies the way Safari works to include that.
The previous version of Glims caused numerous problems when users updated to Mavericks & Safari 7 or to Safari 6.1 on Lion/Mountain Lion.
I've been using Chrome for so long I didn't realize Safari 5 and 6 lacked tab icons as well. I only started using Safari 7 with the Maverick upgrade because I really liked how fast it was working and how nicely it displayed the web (it's a noticeable difference).
I've never even heard of Glims.
Unfortunately this is going to be a deal breaker for me -- bummer.